what i made/used. i tried to make the picture as to-size as possible, but included measurements anyway.
you will need to cut out 4 of these. i made my pattern a little off on one side, so it's best if you cut 2, then flip the pattern to cut the other 2. be sure to cut them all on the same side of the fabric.
now, depending on the type of fabric you are using, there is usually a right side and a wrong side.
sew up one side of it (the smaller side).
now you can see we have a triangle piece two pieces thick with the right sides inside. you need to 