Roll your towel or mat into a tube shape. Using your measuring tape (you can also use a ruler and string) measure around the circumference of the tube. In my case it is 19 inches. I will make my straps 16 inches (to leave a little gap in the middle for the handle)
Create a piece of duct tape fabric that is 16 inches long and two strips wide (approximately 3 inches).
Next I want to create my straps. To do this, I am using some pre-cut accent tape. (A) Lay your 1" wide x12" long accent color strip about a third of the way down one side of your fabric, half on, half off. Fold it over. Do this on both sides. (B). In order to strengthen, make longer, and get rid of any extra sticky bits we take another 1"x12" piece and do the same thing we did in (A) except this time without touching the duct tape fabric. Connect your strip to the inside of the strap and fold over. Your strap should now be 15-16 inches long. (C) Re-enforce the strap you just created in (B) with another piece of tape. Your entire strap should now be doubly thick and strong. (D) Repeat this process on the other side of the fabric. However, on this side your straps will only need to be approximately 6 inches long.
Re-enforce the 6-inch side just like we did with the longer side.
The next step is to add the secret pocket. (A) Use additional 1"x12" strips to complete the border of the fabric so it looks uniform. (B) Lay your piece of pocket fabric in the center of your project. Trim to size, slightly smaller than the area it is in. (C) Tape the piece down on three sides using the 1/2 on, 1/2 off techinque, leaving one side open for the flap. (D). Lay the second piece of pre-made duct tape fabric on top of the pocket to be the flap. Trim to any shape you like. Connect the outside with a thin strip of accent tape.
Tape the inside of the flap as well. Trim the tape to the exact size of the flap so that it opens and closes freely.
Last but not least is the finishing of the strap. Twist the shorter straps in a figure eight motion, creating a loop. Tape the loop to the fabric with a small piece of tape.
Re-enforce this area well by using a 1/2"(w) x 12"(l) piece of tape.
Wrap this strip around the back.
This completes the look and also strengthens the loops.
Now we will create a tiny tongue closer for the straps. I am using two small pre made straps (duct tape wrapped over itself twice - approximately 3 inches in length). Take one of those straps and loop around your longer strap and secure with accent tape. (essentailly it should look like a belt loop)
Give yourself a little bit of space and repeat again with the second mini strap. Creating a double belt loop.
Snip off any extra pieces of duct tape. Secure the loops with a few extra pieces of tape. Trim the strap ends into a nice rounded shape.
Place your towel inside. Pass the long end of the strap through both belt loops then back through one to create a handle.
All done! You have plenty of space to expand and hold onto your water bottle as well!