If they aren't on the bias I don't see any need for a foundation. Could to the 1600" jelly roll quilt too. Just add a few more inches to make it larger.

if you really feel uncomfortable not stabilizing.....maybe a non woven fusible interfacing - very thin - might help stabilize those strips and not add a lot of bulk to the finished product. I use the non woven when doing t-shirt quilts...keeps the knit from stretching.........

I have done one like this without backing and it is fine. I did starch and I did set every seam.

I didn't know I was supposed to use a foundation piece on my first string quilt - turned out fine and has survived many, many machine wash and drys.
Did not starch it either - I never use starch - I think it attracks icky things like silverfish.

I didn't use a foundation piece. I just sewed them together (they were random sizes and widths) then I took my 8 inch square ruler placed it on a diagonal and cut then sached them together with black tied it and gave it to my neighbor. I will see if I have a picture and post it. I was happy with it. Not done the way it should have been but I liked it and so did the neighbor.

Icee

Hi,
I just made three, string quilts and mine were also 2" strips. I just joined the strips, short , med, long, etc. then sewed them side by side. I did not use foundation , I did press very well before I started to quilt it. I made a King size, and two twin size, sold them at our church Craft Sale.

Starch does attract bugs, but if you wash the quilt when it's done it will be fine. Just avoid STORING quilts or fabric with starch in them.