This picture shows a bit of the process I've been using when sewing pieces together for my postage stamp quilt. The box lid holds single 1.5x1.5 inch pieces ready to be sewn together -- the double-pointed knitting needle separates the pieces for block #7 and block#8 (not that they won't eventually get mixed in with block 6 or 9 or 19, but I do sort them separately for each block). The piles to the right show 2x2, 1x1 and 4x4 units waiting to be ironed. I have a lot of ironing to do!
There's a psychological principal at work here -- I don't want to ever finish a block without having a good start on the next one. If I do, I might not ever start the next one! As long as I have the next one started, I trust that I'll keep moving forward on this project. When I sit down to work on the quilt, I usually sew together 2 little stacks of singles (a stack has 20 pieces in it), then I sew up whatever is ironed.