Fold and press (to the wrong side) 1.5cm along each long edge.
Fold and press in half lengthwise and edge stitch along the open edge.
Tip: To help you sew a straight edge stitch, move your needle position closer to the right hand side of the machine foot and use the edge of your machine foot as a guide.
If you like, sew along the other long edge in the same way.
Repeat for the second strap.