round keychain 3d model

I need to create a stl file for a keychain round with letters STO united on upper side, I mean right upper line from S united with left upper part of T and same with O with black letters on yellow background with round edges and 3 layers inside empty for a nfc of 23 mm diameter. 20 layers I guess will be fine and missing layers in the middle. Thank you! Please to put letters in the middle and the keychain must be flatt with a space in the middle of 3-4 layers for introduce in printing time, we paused and introduce a ntc tag covered after that with next layers