If you want to try making this, then proceed to read down below for the full instructions.
Trim the corners of the fabric, then turn it right side out, and poke the corners nicely.
Tuck the seams of the gap and topstitch, then give it a good press.

Image Credit: Hello Sewing via YouTube
Fold the pocket piece in half, find the midpoint, mark, and set it aside.
Fold the long sides of the side fabric to about 3/8, then press.
Press the seams open, then fold it over to form an L-shape.

Pin them together in place, and position the zipper all around the sides of the cross fabric.
*All these images are credited toHello Sewingvia YouTube.
2-in-1 Picnic Tablecloth Bag Sewing Tutorial
