Double your cloth, and lay your present over it. You’re gauging how much fabric you need.
Place the fabric with the wrong side (the back of the fabric) facing you.
Identify the part that will be the top of the bag. Then fold a seam about 1/2 inch, and then fold it again. Press with an iron and pin
With the fabric facing face up, sew a simple hem, double stitching at each end of the fabric.
Fold the bag in half so that the right side (pretty side) of the fabric is facing itself, and make a basic stitch around the sides and bottom like you’re creating a pocket, leaving the hemmed edge open.
Fold it right-side-out, tie a pretty bow, and decorate with gift tag.
How to Make Fabric Gift Bags - https://www.sustainablecooks.com/homemade-cloth-gift-wrap/