This will be just like putting a jigsaw puzzle together. This is how the "funky" swaps end up as we do all different sizes of blocks.
You will want to make "sections" to avoid doing y seams. Lay out the blocks as you want...(you've already done that). Measure all of your blocks, then figure out what size "fillers" you will need to fit in between them to result in the finished size you need. Either sew some pieced blocks in that size, or just cut some plain fabric filler strips to fill in the "holes". These make such great quilts! Yours is going to be great!