Print the insert with PETG, glue magnets to it and follow instructions in the article about printing on T-shirts.
Article: https://blog.prusaprinters.org/how-to-print-on-t-shirts_55588/
Video:
Sheet insert for printing T-shirts
by Jakub Kočí · original on Printables ↗
Fashion / Other Fashion Accessories
♥ 305⬇ 1.1k🖨 8 prints
Print profiles
Sheet_holder.stlDEFAULT
⏱ time and weight estimated after preparation · 1 material(s)
Made to order: we prepare this file when you order, which adds a few minutes before printing starts.
Prints on: A1 mini 0.4PLA
Order this print
Sheet_holder.3mf
⏱ time and weight estimated after preparation · 1 material(s)
Made to order: we prepare this file when you order, which adds a few minutes before printing starts.
Prints on: A1 mini 0.4PLA
Order this print