My favourite method is to place the blocks on the same size batting and trim to required size + seam allowances, and centre and (pin or glue) on backing squares that are 1/2" larger. With two sandwiched blocks together -backings together - join the backings only with a 1/4" seam. Open out, the tops and batting should be touching, almost. Place a strip of sashing/binding (edges folded under) over the seam, and sew down both sides. Keep doing this till you have one row, then make another. You can then join the two rows in the same way, but with a much longer strip of sashing.
If you prefer to use 2" sashing you will need to cut the backing and batting larger.