The most difficult part for me was to draw an actual flip flop pattern (I'm not much of an artist in that respect). I was able to find an image on Google which I enlarged as much as I could, then cut it out, put it down on some pattern making paper, and drew it larger. Proportions were a bit of a challenge! But I ended up with a pattern approximately 17' x 9".
I cut out my top fabric which is a cotton print, and bottom out of burlap. Because there are not really any pillow inserts in this shape, I decided to add some batting and a piece of muslin to both top and bottom, so when I stuff the pillow, it won't look lumpy and I won't have stuffing peaking out of the burlap weave.
I stitched piping to the top fabric and added the straps, which I made from a double thickness of burlap, sewing through top fabric, batting and muslin. Next I measured around the entire flip flop form to determine the length and cut a 3-1/2" strip of aqua fabric to be used for the thickness.
I sewed the aqua strip to the top and bottom portions of the flip flop, similar to a boxed cushion, leaving a space open for stuffing. I then stuffed, fluffed to shape and hand-sewed the opening to close. The one shown below used a coordinating fabric. What do you think? Kinda fun, huh?