Start by cutting the top of your pillowcase (where the envelope forms) so that you're left with a simple bag with an open top.

Cut out the front panel of this trimmed top.

Cut two strips of 3" wide from this panel.

Fold the ends of the strips inside, about 1/4". Press and sew.

Fold the strips in half, wrong sides together.

Pin one strip to one side of the pillowcase, right sides together and the other strip to the other side of the pillowcase, also right sides together.

Sew with 1/2" allowance then serge the raw edges or use a zig zag stitch.

Press the casing up so the seam is now pressed down inside the bag.

Press the seam and top stitch.

Using a safety pin, thread some ribbon through the casing, starting on one end and going around the entire casing until you are back where you started.

Grab another piece of ribbon and start threading it through the casing, starting on the opposite end and thread again through the entire casing until you're back where you started.

Tie the ribbons together into a knot, at each end of the casing.

Use these knots to pull the ribbon to close the bag in one go.

To open the bag, simply grab the opening with both hands and pull.