The way I did this was to create all the individual sandwiches (back rectangle, top rectangle and a piece of batting of the finished size of the rectangle so that it wouldn't be in the snipped edges). Then I quilted an x on the rectangle and maybe along the seam allowance. Then I sewed the blocks into rows, etc. The seam allowances are more than 1/4 inch--maybe 1/2 to 5/8"? Once sewn together you cut just shy of the seam around all edges and wash a couple times. Sorry so vague. That was about 10 years ago. You can google rag quilt and get more details.
Now for the basic quilt, I found the pattern. It's called Boca Blocks.
1. Cut 27 rectangles. 6.5" x 10.5" in the amounts of your choice. [Scrappy: a total of 27 different fabrics; 4 fabric: 7 blocks in color 1, 2, & 3 and 6 blocks in color 4; 2 fabric or light/dark combo: 14 blocks color 1 and 13 blocks color 2]
2. Stack your fabrics right side facing up, in the following order: [Scrappy: Just stack them!; 4 fabric: fabric 1, fabric 2, fabric 3, fabric 4, fabric 1, etc; 2 color: 1, 2, 1, 2 etc]
3. Sew units together end to end (short end) so you have one continuous strip, 27 blocks long.
4. The quilt is made of 6 vertical rows of blocks. Cut the long continuous strip into 6 strips as follows:
a. Count down 4 blocks and cut the 5th block in half. This is Row 1.
b. Row 2 starts with the half block and count down 4 more.
c. Open the seam and start row 3.
d. Continue in this manner until you have 6 rows.
5. Sew the strips together.
6. Layer, quilt, bind.
ta da!