For this example I used a medium to heavy weight interfacing. Before beginning you need to determine how large you need your interfacing to be. To do this you need to take the size of your fabric squares and multiply it time the number of squares you have. For example. I have 14 squares per row. I multiply this time 1.25 inches (the size of the squares) and I end up with 17.5 inches.
(14 x 1.25 = 17.5) I cut my interfacing 1 inch larger to give myself a little extra space to work with. Total my interfacing was 18.5 inches square. You certainly do not have to make your interfacing larger because prior to fusing your squares you will need to trim off the excess interfacing. Either that or you will have to clean off your iron.
Once you have the size you need cut out, flip the interfacing over to the non-fusible side. Using a straight edge and a pen or pencil draw a grid onto the back of your interfacing.
I used my personally designed duck-tape pen.
If you don't have one that's OK.
I am sure a plain ordinary pen works just as well.
Be sure to space the lines out the size of your squares. My squares were 1.25 inches so I drew 15 lines 1.25 inches horizontally and vertically to create my grid.
Now that your lines are drawn you can flip the interfacing over and start laying out your design. You should be able to view the grid from the opposite side. Lay out your pieces according to your design, lining up the fabric along grid lines.
Once your design is aligned carefully (This is an important step. ) Very carefully press and fuse your fabric to your interfacing. Be careful not to "iron" your fabric a slight movement will cause those tiny little blocks to shift. If the blocks shift this will cause you great pain and suffering as you try to gently pull off the fabric pieces before they cool. You will pull too hard and find out they are permanently fused thus tearing your interfacing. This will result in you starting over from the beginning. This is all theoretical. It never happened to me, ever.
After you have carefully fused your fabric, the fun really begins! Now it is time to sew! Flip your design over and you should notice the interfacing wants to naturally fold along the rows. Isn't it great! Fold the interfacing along your line, right sides of fabric together. Pin every couple of blocks to insure you squares stay aligned as you sew. Then sew 1/4 seam down the side of your column. Continue to sew your rows across the block. Your design will then look something like this...
|after sewing--seams create tube|
Now you will need to cut the seam allowance open. You will need a small pair of sharp scissors. Large scissors work but they are a bit cumbersome with the tiny seams. Insert the scissors into the "tube"(for lack of a better word) that you created when the rows were sewn. Cut as straight as possible, through the tube, down the interfacing on the backside, being careful not to cut through your stitching. Once the seam is cut open press the seem open.
|seams pressed open|
The reasons for this are as follows... One. An open seam will be much easier to line up when you sew your columns. Two. Sewing through all those layers is difficult and exhausting. Three. Quilting through all those fabric lumps and bumps is a nightmare. Your long-arm quilter will thank you.
Pin your rows in several strategic locations, insuring your seams line up. Sew down the rows at 1/4 as you did before. Once all of the rows are sewn cut seam allowance open. Press seams open.
Whoop! You have done it! Congratulations!