This design is based upon my cinch sack project. This project uses the same methodology for creating the holes for cordage and for placing the cordage. Please take a look at Making a cinch string sack from a pillowcase is a cinch (https://www.instructables.com/id/Making-a-cinch-string-sack-from-a-pillow-case-is-a/ ) if you need more clarification than this Instructable provides.
The project also uses the Reinforced fabric hole which can be found at https://www.instructables.com/id/Reinforced-fabric-hole-Old-style-button-hole-or-ey/
Step 1: Tools and Materials
Extra material for eyelets
Step 2: Select a Pillowcase.
Step 3: Open the Top Seam
Open the top seam of the pillow case.
There are different ways a pillow case may be constructed. If you can not open the top seam all the way due to a seam running up the side of the pillow case then you will have to open the seam on the side and redo it so the case functions as you need it to. Details for how to do this can be found on the cinch sack tutorial https://www.instructables.com/id/Making-a-cinch-string-sack-from-a-pillow-case-is-a/
Step 4: Placing the Reinforcing Material for the Cinch String Holes
I decided to place holes in what would be the top corners of the pillowcase.
Detailed Instructions for creating material reinforced holes is found at https://www.instructables.com/id/Reinforced-fabric-hole-Old-style-button-hole-or-ey/
Cut out your reinforcement material and attach it face down to the inside of the cordage channel. The image shows the proper placement of the reinforcement material but it is not sewn fast. You will only sew through one layer of the pillow case to attach the reinforcement.
Step 5: Attach the Reinforcement and Cut the Holes
Cut the center "x" to form the hole.
Turn the pillow case right side out.
Step 6: Pull Reinforcement Material Through the Hole
Step 7: Finish Cinch String Holes
Step 8: Close the Top Seam
Step 9: Create the Bottom Attachment Points
Sew the reinforcement through both layers of the pillow case.
The goal is to have all the reinforcement material visible on one side of the backpack. Your finished backpack will look like a rectangle with a hole in each corner.
Finish off the hole as explained in the reinforced fabric hole tutorial.
Step 10: Add the Cordage
Place the cordage through the end of a paper clip or safety pin, fold the cordage over and tape it fast.
Insert the paper clip into the hole and work it around the circumference until you reach the same hole you put it in.
Pull it out of the hole.
Remove the paper clip and tape.
Tie the ends of the cordage together. (see pictures)
Snap on carabiner.
Repeat this process through the second cinch string hole of the bag.