Have you read The Nameless Flower, it isn't exactly a slow burn but it definitely has yearning and is definitely one of my favorites.
muhyeok and naui: my irresistible neighbor
i think it has a good mixture of both? imo, if you get through the pre stages its basically just 40 chapters of them loving each other
Manhwa/manhuas
https://www.mangago.me/read-manga/incidentally_dyed_by_spring_s_love/
https://www.mangago.me/read-manga/cosmic_boy/
https://www.mangago.me/read-manga/circle_wang_zi_ying/
https://www.mangago.me/read-manga/minority_1/
https://www.mangago.me/read-manga/the_king_of_loving_love/
Mangas
https://www.mangago.me/read-manga/koimonogatari/
https://www.mangago.me/read-manga/hishakaishindo/
https://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/
https://www.mangago.me/read-manga/smoke_blue_no_ame_nochi_hare/
https://www.mangago.me/read-manga/jealousy_scarlet_beriko/(TW)
can anyone recommend me a slow burn bl manhwa or manga that has yearning in it tooヾ(❀╹◡╹)ﾉ~