Double knit throws wear like iron!

I have made many double knit throws for charity.

Assuming you have a sewing machine that will stich thru a base layer of PREWASHED medium canvas or heavy denim and the double knit fabrics:
(1) Cut double knit into 2-3" bias squares. 100% accuracy not required. I have used some circles as well.
(2) Hem your canvas to rectangle/oval/other desired shape and size. My largest are about 18"x36".
(3) Pencil stitching lines on base fabric top side. Lines should be 1/2-1.5" apart. Lines can be curved, if you feel dramatic. You can mark what color of double knit you want in a specific area or just have random placement.
(4) Stitch the knit pieces to the base on the diagonal. I like to overlap the tips by 1/4-3/4". I stitch 1/2" from the outside edge.
(5) One of the easiest 'designs' is to stitch a circular patterm from the center, and then finish the rest of the mat parallel. Much depends on your machine's throat space. Backstitch at edges/ends.
(6) Additionally, if your knits are the lightweight types, tuck small pleats as you stitch. On most uses, I place a mesh carpet mat under this mat. These mats "shake out" easily. They are tough, hold lots of debris, yet comfortable to stand on if you have a stone floor. Am planning to make a mat from my silk scraps for my bathroom.
If you desire, you can line the base of the mat. Most of mine are made on a commercial walking foot machine with #69 upholstery thread. Some were made with poly cotton thread and are still in use. If you only have a standard machine and thread, you could double stitch pieces.
(7) Another variant I have used for lightweight double knits is to cut 1 1/2-2" bias strips, gather down the center and then stitch to the base.

Hope this is clear-e-mail if not. Happy re-purposing.