me too. in general i use the jisho meanings for radicals, put them as synonyms and learn those. in this case i know 頁 as “page”.
this pair of kanji annoys me too because they’re both “origin(al) page”, which doesn’t tell me much in the first place. i therefore just remember that π is the number that stubbornly goes on and on and never ends. that usually does it for me,