I figured this out when I was making quilt as you go rag quilts. I made a frame around the quit using solid square blocks. Maybe I can explain it better. When I sew a row of blocks together I add a block as wide as I want the border to be but the same size as the block lengthwise. The first row will get a block added to the first block and last block as well as on the top. Each block on the top row will have a border block sewn to the top of the block. Reverse at the bottom row. Like adding another block to the row but it isn't a pieced block just solid fabric.