I saw this a day or two ago and can't remember where but I lol watching it:
1. cut your fabric into two squares (start with two pieces of paper and sew on your machine)
2. put right sides together
3. sew all around the four dides
4. Lay flat on table draw a line from one corner to the other (a diagonal line)
5. nip off those two corners
6. turn the square over to the other side
7. draw a line diagonally across the square to the untouched corners
8. clip of those corners
9. cut along the one of the diagonal lines
10. turn the square over and cut along the other diagonal line
Honestly it makes a tube, you can iron it gently so the seams lay flat and then use some yard stick or ruler to make strips of diagonal whatever width you'd like.