So anyway, using dropcloths (the linen-y texture and oatmealish color of which I love) was a perfect solution. A perfect $10 solution.
A little help from Allie (Todd's coworker/my sewing buddy) and I was on my way. The first one took a long time to measure out, and I predictably got confused with the math and need to enlist a little velcro to help the backs stay shut. But on the whole, I am so happy with how they look, and feel TOTALLY accomplished for coming up with an idea, plotting it out and making it happen!
It's official: sewing is fun!
My pillows were 26" x 26" and I measured 28" for the big square and should have done about 15" x 28" and 14" x 28" for the backs. (Or even a little more. The backs fluff out in the middle, not that anyone sees. That's where I need a bit of velcro.)
There was only a small mess left in the kitchen after: