Start with cutting 3"x5" (roughly) scraps of old t-shirt or jersey fabric. I think I used 7 or 8 different colors and I cut out 4 scraps of each color.
Using a regular straight stitch, sew two scraps together on one end.
Sooo, I cut off what I could from underneath and went back to a normal stitch length.
And after trying again, my seam was all over the place.