Heres a video showing how to attach the print to the T-shirt.
https://youtu.be/x4EiUu33GbM

Lego design modeled here:
http://bricks.lapinoo.net/

• Follow directions on page for testing bricks on your printer.
• create your own underlying design.
• use regular size bricks to export as stl

In Cura adjust the z scale to 130 percent to increase the length of the lego top dots.
Drop the lego stl below the cura build surface about half way through the brick this will avoid using to much plastic and also bypass printing the hollowed out surface of the lego.

-Follow directions for printing on tulle here:
https://www.youtube.com/watch?v=CjH5KGw3Psw

• I usually lay down my tulle after the 2nd or 3d Layer. Use "Pause at Height" in Cura.