Is there some kind of easy rule or guide for when to use “i” vs. “ii” and other close pronunciation/spelling issues? Or does one have to memorize the spelling of each word, and thats it? I already know most of these low level words and can read and say them, but havent had to write before, and most of my wanikani errors are things like this, rather than not remembering the meanings of new kanji im being presented with, which can be annoying. Honestly if there were a setting to accept errors in spelling in which the pronunciation is essentially the same, like 水 sui / suii , or 大きい needing to be ookii rather than okii or oki or ooki, I’d take it. I do get the its not EXACTLY the same pronunciation and thus spelling in hiragana, but to be spending most of my time in a kanji program fixing errors on precise hiragana spellings… well if theres a little guide out there somewhere (maybe written in this forum in response to a similar question?) I’d appreciate it. Otherwise waninkani is great. (: Thanks.
I can only think of a couple of examples of kanji which have a long-i sound concealed within their readings. If there’s a long-i sound in a word, it’s nearly always either explicitly invoked by the okurigana, as in 大きい or 良い, or it comes from smooshing together the readings of two separate kanji, as in 委員 or 黄色.
So I’m afraid there’s no shortcut beyond just “learn the words”. You’ll get the hang of it eventually.
おき, おおき and おおきい are not the same pronunciation, and you’ll need to learn the difference or you’re gonna have a hard time making yourself understood.
IMEs tend to be pretty unforgiving. If you try to get 大きい by typing おき, your average IME is gonna look at you blankly and go “… did you mean 置き?” You need to be pretty precise with your spelling, and WaniKani is doing its best to teach you good habits. If you bypass WaniKani’s insistence on getting the spelling right now, you’re only going to be spending most of your time in an IME fixing errors later.
Of the top of my head I can’t remember any common kanji that have long い in their reading, except 小さい（ちいさい）. So you could by default assume short い.
Vocabulary with long い, such as 大きい, should not be a problem for you in WK reviews because you just need to type the hiragana you see on the card as is “oo-ki-i”.
It’s a fairly common pattern in japanese adjectives to end with long i, particularly after し, for example:
うれしい
さびしい
おいしい
むなしい
こうばしい
A more general piece of advice regarding learning Japanese: don’t get frustrated if you keep making mistakes in reviews. Rather pay more attention to them and try to find patterns. If you make typos in okurigana, slow down when typing that part and make sure you get it right. If you forgot if the kanji had a long sound or not then you simply didn’t remember the reading yet. It’s the same as if you mixed up eg かん/ばん. Go back to the mnemonic, look at vocabulary and try to remember it correctly. Don’t keep rushing through and trying to guess. It’s not about guessing. You need to remember the reading.
I actually do speak a decent amt of Japanese and have no problem making myself understood, probably my spoken pronunciation is mostly fine. But I have no writing experience and no current interest in learning it, just want to read kanji and a little frustrated that most of my errors are minor spelling differences rather than kanji meaning/reading issues. Wish there were a multiple choice option or similar or slight fuzz factor for the readings rather than precise spelling. But anyway I do get that its not BAD to spell correctly, and of course its helpful, so Ill just deal with it. Thanks.
Thanks, thats helpful. As I just wrote in another comment, Ill just deal with it then. 
Its manageable and Ill work on it. True about finding patterns, Ill look for it.
Other than conjugation, some of them probably come from etymology.
On the top of my head, 陥る, 陥れる. Well, 小さい too. Anyway, remember, at least because it matters with IME.
漢語 probably doesn’t just get ii.
Yeah, the way Chinese syllables are rendered in Japanese doesn’t really allow for a single on’yomi to contain ii. Every on’yomi is 1-2 morae, which means means 水 could never be suii, because that’s three morae.
I mean, technically, you could have kii, rii, shii and so forth, but fortunately, there don’t seem to be any on’yomi like that.
Edit: Apparently there are a few exceptions, such as 弑 (しい) [murder one’s lord or father], but they’re quite rare.
So, I guess the rule of thumb would be “In on’yomi, never use ii if it would result in more than 2 morae … and even if it wouldn’t, it probably still isn’t ii, unless you’re planning to commit patri- and/or regicide.”
LOL thank you thats helpful.
I just got “chiisaii” wrong. Just annoying. I absolutely know how to say it correctly, and I can easily recognize and read it in both full hiragana and with kanji. But I cant spell it because I’ve never stopped to think if its ちいさい, ちさい, ちいさいい, whatever. Booo.
Are you overthinking it? For the most part Japanese pronunciation is consistent with spelling.
Whenever I hear a new word I can spell it correctly and look it up in the dictionary. Unlike English where the spelling could be really unexpected…
Thats true, I also dont have a problem finding Japanese words I’ve heard in the dictionary. Although actually I probably do sometimes try a few combinations before I hit the right one. Anyway so hopefully this wont be an issue that will get worse as my kanji advances… just a few spelling patterns Ill need to get accustomed to.
I suspect you’ll find it gets better.
Eye wood argu that propper speelling is importent two learnn.
As others have mentioned as well, it is not just a matter of “spelling”, pronunciation is different as well. It is something I had to work on improving after having not paid it a lot of attention initially and was something I was frequently corrected on. At some point you will also reach the point of hearing and noticing the differences. Correctly spelling words and correctly pronouncing words will reinforce each other.
I’d agree, but I feel like you’ve mildly undermined your point by writing this in English, because I can read that just fine. 
You were right about this, it’s already getting better. Seems that it was a unique issue with the i’s. And with other mild spelling mistakes, like using a double or triple n in some words, I’ve seen that wanikani kindly will prompt you to fix it rather than calling it an error.