Frisco Craft Heat Transfer Vinyl Transfer Tape - Clear Iron-On Tape Patterned HTV & Adhesive Paper for Large & Small Projects, Heat Press, No Residue, Reusable up to 5 Times, High Tack (12" x 50 ft)

You need a heat transfer mask. It’s like transfer tape but for specialty HTVs that do not come with a carrier sheet. I like the Frisco Craft one. Siser TTD always gets mixed reviews but it’s another option. Or you can reuse old carrier sheets from HTV if you have it.