i always bring this example up - but acknowledge the friendship, but then also acknowledge your interest in him (don't come off too strong, just say that there's some feelings/interest involved). then ask about his thoughts on that, to open up the floor for discussion without adding pressure on him or the friendship
okay i thought about it and how about prefacing with a request for a mature adult conversation and “ik we don’t rlly talk about this stuff but i think ive been developing feelings for you, and i wanted to wait until i was less isolated to make sure they were real. pls don’t get scared off bc regardless you’re a really important person to me, but i was wondering if you felt the same and if so, if you’d want to talk about that.”