Zappycat, if you're getting a set of flannel sheets for $11.99 with 30% off, you're getting an excellent deal! The flannel sheets make excellent backings and you can use the pillowcases 'as is' to hold/match the quilt. The fitted sheets - cut the elastic off, open the darts and lay it flat and you have another backing, plus scraps.
Buying a set of flannel sheets for $8.40 is better than any good will or thrift store buy.