I make these shirts for my wife using 4 mm and 3 mm crystals.
You use a plastic transfer sheet and an iron set to 350’ F for 12 to 20 seconds.
All the crystals are heated and transferred at the same time.
You make a reusable stencil.
Add the components to the stencil right side up, pick up everything with the sticky sheet, apply to material, heat, cool pull off the sheet.
Now I was thinking why not SMDs to a PCB.
I’ll give it a try.