Now you'll sew the columns together to make the quilt top!
This is the only time I'll pin while sewing the quilt top. Because you're dealing with a lot more fabric and it can shift like crazy, I pin every few squares, as shown in the second picture. :)
Start by laying column 1 on your work surface right side up. Lay column 2 on top of it, right side down. Line everything up as well as you can, and then pin.
To properly sew this, get the top corner secured in your machine, and pile the rest of the column into your lap. You don't want any of the fabric hanging off the table - it causes serious pulling and will make you sew very crookedly and puts extra pressure in your machine. So make sure you're not letting the sewn fabric pile up behind the machine and the fabric that's feeding through is supported well. If you feel any tugging, stop sewing and adjust the fabric. (Pictures 3 & 4)
Keep sewing on the additional columns until you're done, and remember that rolling comes in handy! (Picture 6)