I used a duvet cover that I bought from ebay. Put a batting in it and quilted it up. It makes a great picnic quilt. It's a madras plaid print and it kind of looks pieces without the work.

I have a picnic quilt in progress (several weeks now). The top is poly/cotton (which I inadvertently bought at auction as quilting fabric). I'm using the same type of fabric on the backing (I have lots of it.) I did not want to quilt it heavily, but wanted it to stand up to repeated washings. I bought a polyester blanket to use as the batting. I posted questions here regarding using that and all agreed that it should work and not shift after washing. The other suggestion was to use a mattress pad for the batting, which I am going to do as I have one in the top of the closet that is almost new, but wouldn't stay on the bed.

As for you first question regarding the backing, I think a flannel backed tablecloth would disintegrate in the washer after it was pierced by the needle in quilting, unless of course, your flannel backed tablecloth is a lot better than the ones I have.

My experience with using a quilt on the wet ground is one outdoor concert many years ago. My date brought the quilt and I brought the plastic to put under it (He hadn't thought of it.)

bk

Thanks everyone for your comments. I think using the vinyl tablecloth under the quilt rather than as the quilt backing is a great idea. I will gift one of those along with the quilt.

This landed in my mailbox today. From Hacks and Hometalk. Funny timing.
https://www.hometalk.com/29119202/waterproof-blanket

To Mindless: I loved your story!

I used Nikwax to waterproof fleece used in felted wool mittens that I made. The waterproofing on an old waterproof fleece wore off and I used Nikwax on that too. It worked great. You might try the cotton version Nikwax on it to help keep it dry. I’m sure there’s a version for flannel too if you go with that.