I have never quilted anyway but a block at a time. I've never had a problem with corners and have used many different patterns, both setting with sashings and alternating plain with pieced blocks. I have also done this with blocks set on the diagonal, using sashings and corner blocks.
If you will PM me, I will give you a detailed description of how I do it. Not the only way, and probably not the best way, but it works for me. I'm working now on a king-sized quilt for my daughter. She bought all the materials, and she is quilting some of the blocks - after I showed her how o do it.