Then piece the top pair and then the bottom pair following the instructions here.
Once you have pieced them, it is time to join them together for form a 4 block:
Lay the pieces right side together (RST) matching the seam that you want to join:
Starting with the middle seam, put a pin through the seam. I use these pins for the patchwork, they are sharp and long so easily go through the seam.
Align the seams up as much as possible and put the pin through, adjusting the fabrics so that the pin goes through both of the seams. It should look like this when pinned:
Add pins at either end of the seam to be stitched:
This works no matter how many blocks you are joining! Stitch along the seam, back stitching at the beginning and end:
Make sure you iron the block on both sides!
And you are finished!