If you have an IWB/AIWB holster you already like:
https://www.crossbreedholsters.com/p.../liberty-band/
Put the “band” on over your underwear/undershirt, at the same height as your normal belt. Put on pants and tuck in shirt over the gun. No need for a heavy gun belt but something slightly stiffer might help. The advantage with this system is you don’t have any clips showing on your outer belt. Also don’t have the issue of trying to tuck a shirt between a holster body and a clip like most “tuckable” holsters.
Crossbreed has a good belly band using a Velcro/kydex holster that you’d wear similarly.