I would try straight line withthe walking foot on but instead of in the ditch just wiggle through the middle ina rough grid. It's quick easy and surprisingly effective.
I would trim the wadding to the same size as the blocks. Attach one side with basting spray and then use pins to align the pieces front and back using the seams as a guide.
you don't say what QAYG method you are going to use. You probably need some kind of grid for this one to retain your sanity. A 1" on the front ( cut 2" strips and sew on with a 1/2" seam allowance to both front edges). Your blocks will take it and look like they are being viewed through a leaded window if it is dark enough. Cut strips 1 1/2" for the back and fold and press them in half wrong sides together. Stitch them to one edge on the back through all the layers, turn the folded edge across and carefully top stitch just on the edge. This will give you a half inch grid on the back with a one inch grid on the front and a pair of stitched tracks 1/2" apart down the sashing grid on the front but it is zero hand sewing required.
Does that help? I love split nine patches. All the ones I have done have been single sided and meander quilted, but I haven't made any big enough to warrent a QAYG approach. let us know how it turns out!
best Becks