Cut each end of the Ziploc bag to open up the sealed edges.

Use three small pieces of tape to tape one edge of the Ziploc part of the bag down on to the Ziploc bag.

Cut a piece of tape the exact width of your bag.

Lay that piece of tape on the inside edge of the bag.  Place it just at the edge, right over the ziploc portion of the bag.

Flip the bag over and fold the tape over until it meets the edge of the ziploc - essentially sealing in the ziploc edge.  Repeat the process on the other side.  Cut a piece of tape that is about an inch wider than the bag on both sides.  Place this piece of tape at the edge, overlapping the piece you just placed

Flip the bag over, fold the ends in and seal the sides.

Now it is time to add the strap.  Lay the strap in and place two pieces of tape horizontally across the strap.  Be sure that your strap is laying correctly.

Place two more small pieces of tape vertically to secure the strap.

Cut a piece of tape the same width of the bag.  Line it up with the top edge of the tape on the other side of the bag.

Begin covering your bag by going back and forth with colors of your choice.

Continue covering and trimming until both sides of the bag are covered.

You bag is essentially finished.  If you like, you can add a pocket like I have done.  To do so, fold the bottom 1/3 of the bag up onto itself. Use two pieces of tape to seal the pocket using the half on-half off method.

Again, you may leave your bag just as it is.  Or you can, as I like to, create a pouch effect by creating small triangles at the corner and "pooching" out the bag,  Use a piece of tape to secure each corner.

Run another piece of 1 inch tape aong the bottom of the bag to seal in those corners.  You may need to place a small piece of tape inside the bag to cover any xposed sticky parts created when you pooched out the bag.

If you like you can use a piece of sticky back velcro as a closure