I watched a video (see below) on using a peg loom and eventually decided to make one for myself. The loom I made can be extended to any width. I love that the parts can be easily stored after a project is completed.
My initial goal was to make a big rug for my living room, but after working on the much smaller brown and natural rug shown in the photo today, I think I will hold off on the large rug. The yarn to coat (YTC) project I began earlier in the year will be finished with the peg loom.
Here is the link for the stereolithography files to make the loom.
Update October 11, 2017
I made a comb for the loom. The teeth on the side are for combing yarn to facilitate felted joining. Here is the link to the .stl file.