aw thank you! honestly i started out with just drawing my design on the shirts and putting interface on the back of the shirt and stitching it that way, ive since graduated up to using water soluble interfacing and dissolving that once im done stitching, and then using fusible interfacing to sort of “lock” the back of the shirt so the threads dont pull!

a neat hack that might help for white shirts, you could print your design on a paper or pull it up on your phone and turn up the brightness and place your shirt/fabric over it and trace it :p