It is not hard to make this but you need a few precautions because it is stretchy and it can “crawl” when you sew on it.
1- Lay your fabric out flat and make sure it is squared- That means straight lines the exact same on all four sides. .
2-Cut one side on and then lay the other piece on it (in sides out) and smooth it down carefully and cut the second piece to match it exactly.
3-Then pin it together with straight pins vertically to the edge. Put the pins about 5″ apart and make sure it is smooth.
4-Loosen the pressure on your feed dogs one number.
5- Sew around it leaving about 7 inches open in the middle of one side.
6- Turn the blanket right side out.
7-pin the opening with a couple of pins with the seam tucked inside.
8-Top stitch all the way around the blanket about 1/4 ” from the edge.