If you’ve got full boobs but they’re more flat on top, like a tear drop shape, I highly recommend the t shirt bras by Dorina. (I think they’re called Michelle?) They’re completely unpadded with a soft but sturdy cup.
I got mine from ASOS for £14, and a strapless multi way one for like £30. I wear a 32C and seriously, they fit and support the fullness on the bottom, yet sit flush to my chest at the top. No empty boob shell!!!! 🙌