We found that a 5% polyester/95% cotton blend worked best. The polyester seems to melt at the edges of the cuts, sealing them against fraying. Cotton works as well, but care has to be taken not to fray the edges of the cuts.
Super-cool technique–I’ve been dreaming about ways to layer lasered fabric without the enormous time commitment of traditional quilting. This is one I’ll definitely try.
The OP was done on a maker space laser, so settings wouldn’t translate well. I’ve seen some fabric stuff in Beyond the Manual, but not a lot. There have been a fair number of settings for felt, including polyester “felt” so searching for felt may be the best place to start.