Step 7: Continue binding your envelopes
Once your corner is secure, (I reinforce about 4 holes down using the technique in Step 6) sew down the pre-drilled line of the envelopes in a back and forth manner to the opposing corner. You should have a stitch that looks like that in Picture 1, with every other space empty.
When you reach the other corner, remember to reinforce the stitches on the end and then begin sewing back up to the first corner. When you make this pass, you want to loop the thread around the outside edge of the envelopes. If you find your sewing pattern to not match up with the empty spaces of the first, just double-back until you've enclosed all the empty spaces with thread.
NOTE: If you find your thread starting to tangle, allow the needle and thread to dangle freely from the envelopes. This will unspin the thread and make sewing easier (picture 2).