what I do after I do a layout is stack each row (being careful to be consistent that I move from left to right), then put a safety pin in the lower left corner of the stack. Then I go from top to bottom 'collecting' stacks. If I am not going to sew them immediately, I pin my stacks together. sometimes I also use post it notes on each stack. Of course, you still have to remember what the pin in the corner stood for, or write it down and attach it.