This is a derivative of Charlotte's excellent Ult-shirt, with a little depth. I printed it in PLA directly onto a cotton t-shirt. To do this, do yourself a favor and get some double sided tape. After a failure using binder clips and rubber bands, I used double sided tape to tape the t-shirt to a 9'x9' piece of plywood. Here are my steps:1. Cover one side of the board with double sided tape. 2. Slide the board inside the shirt with the tape side facing the underside of where you want the design. 3. Press it in place starting from the top, removing wrinkles as you go. 4. Then raid the kitchen for a square metal baking pan slightly smaller than the plywood. 5. Drape the spare fabric in the pan. Tuck it in so that there is a minimum of bunching around the edges.6. Tape the board tight to the pan at the edges, taking care to not cover where the design will go.7. Drop your print bed until there is room for you to slide your assembly under the head.8. Put some more double sided tape on the bottom of the pan, and tape it centered on your print bed. You remember which side is the top of the shirt, right? 9. Carefully raise the bed until you pass the sliding paper test, but use something slightly thicker like an index card. 10. Carefully check min, mid, and max positions for x and y, dropping the bed if you must, then using paper shims under the pan for fine tuning. (I don't want to re-level just for this.) 11. Slice the design with Cura. I used Layer Height .1, Shell thickness .8, Bottom/top .8, Fill 30%, Speed 60, Temp 220, Initial layer .312. The default start code will ruin your day, so edit the start code or the generated gcode. Replace the G28 Z0 with G92 Z0 so that Marlin accepts the current z height as the zero point.13. Start the print. I turned the heat up to 230 and the extrusion to 125% for the first layer. On the theory that I would get better adhesion to the cotton. I turned it back down to 220 and 100% after the first layer completed.14.Stick around. If it is going to fail, it will fail spectacularly. On my first try (with binder clips, not tape) the head caught on an errant blob, pulled the pan sideways and dove through the fabric.15. When the print is complete, you will have to be very careful removing the board from the shirt, or you will crack the print, or separate it from the shirt.16. If it does separate, you can use a little bit of fabric glue or school glue to get it to stick, if you don't mind making it permanent.17. Wear proudly.18. Since the print won't do well in the wash, just carefully peel the print off of the shirt before washing the shirt.