What I do is keep a diary where I try and describe what I did that day and then amend it after.
My process is (1) Write down the date, what I did, how I felt, and maybe what I plan to do later in the day/ tomorrow. (2) Plug that into google translate to make sure the meaning comes out alright and (3) put it through https://bunpo-check.com/ . It might not change what I say to the most natural way to say it, but I’ve found its a great way to make sure I’m using grammar points correctly. The AI will give one explanation of a change per day, and you can chat with it a bit to get help saying what you mean to say. (4) If I’m feeling extra adventurous, posting on HiNative after all that is a great way to find out how to naturally say what I mean! The Japanese speakers on there are very helpful.
(Speaking of HiNative, eventually you could try and reply to questions about English in Japanese to practice as well. Its a great way to tell if you articulate yourself well enough to be understood.)
This process has really been working for me. However, I’m someone who chats to myself all the time and loves a good over-explain sesh, so its quite natural and enjoyable. If you’re looking for a pen pal service I’m sure someone will recommend one soon!
If you’d like, I can post what my diary entry was today. This, though, was my first attempt at complex/ unprompted sentences…
Awful awful awful but I learnt a lot from it. I actually plan to continue the story next Feb to see what my progress has been! Doing things badly is how ya learn, so go make a mess of it 