you (can) have your batting/backing a little bit larger than the top (if you plan to do extensive quilting on the block-then trim them to the same size after quilting- but i think usually for qayg it's not as necessary- unless it's really large- or you are doing very dense quilting.
you are kind of (over-complicating) the process...often quilted blocks are then put together with sashing strips- but there are numerous ways to go about it- the Leah Day method is a good place for tips/hints, also- 'the Cotton Theory' technique- Elenor Burns has a (6-Hour Quilt) that teaches another method- that's fun & easy- none of them involve any hand sewing or as many steps as you are (envisioning)