siss--I have made levi "tarps" for years. The first one I made I was a good little girl & cut all the old jeans the same size. BIG mistake-as now you have 4 layers of denim to sew thru. Even with a jeans needle, I broke quite a few. So finally it dawned me to cut the hems off-using siccors cut along each side of the leg seams, -(just a little)-now rip the legs up towards the pocket. I than cut off the leg from around the top. Sometimes the pockets come out also.
Now back to the cutting board.-I line up one ripped side on a line & than cut the long strips of levis into the same length. I do 10" as it is a nice round number. I than use my serger & go around each piece. I than sew the 10" sides together-as long as I want. (Have been known to lay them on the beds to measure). Do several strips & than sew the strips together.OOOPS forgot-I usually use a 1/2" seam, but it doesn't matter.
If one length is too long just cut it off & serge the cut edge. When I sew the seam, I than fold the serged edges to one side & sew on the serged stitches. No pressing involved!!!!
The beauty of doing it all this way, is you have different widths & not all of your corners are a 4 corner match. I think it is like a brick design. These hold up really good & are VERY heavy. Mine have been used to lay under tents, over coolersto help insulate them when camping, on the grass for picnics, on the cruddy tables @ picnics, on the muddy ground as a tarp to change tires, on the fishing bank to keep the stickers out of your britches, as well as whatever else you can think of!!
To clean them up- you just shake them out, & was & dry. If there is a hole on one of the pieces, just sew on an applique!!!
Good luck!!