First, cut 2 pieces of duct tape like this.
Make sure they're long enough to fold and still be a good size.
Then connect them.
Fold them in half. Make sure to test it before you actually connect the two sides.
Cut a piece of the other color of duct tape that will fit squarely in the middle of the piece you already made.
Then attach that piece to the front of your existing piece. Make sure it is in the middle before you paste it down.
Fold the tip of your duct tape pieces like this.
Then cut where you have folded to make a slit.
Cut a thin piece of duct tape like this.
Fold it on half and slide it through the slit you made on the other piece.
Cut 2 small pieces of Velcro, one for each side. Then attach them to the ends of your strap.
Now you're done! You can write whatever you want on it, but make sure to use permanent marker.