I can't remember where I saw, heard, read this method (or who to give credit to), but this is what I do.
(works great for placemat)
Cut strips 2 1/2" or fabric and batting about 13" long
Put a layer of fabric face down, a layer of batting then a layer of fabric face up. I sew down the left side to keep everything in place.
Next, from the bottom put batting, fabric face down the first piece, then fabric face down. Sew 1/2" seam then fold the batting, fabric out from the bottom (finger press or iron), and the fabric from the top. Now you have a placemat started and continue until you're done.
I hope this makes sense :). Once I'm happy with the size (usually 12-13" X 17-18") I trim and bind. I guess you could round the corners and use bias binding...that might look like too.
Goes really quickly.