I had actually figured that if you put the main square together as one block and then one half of each heart in one color together as another block, they could then be put together as a set of 4 blocks.
If you can see the red dashed lines on the draft pictures, those are the sets. Then it's a matter of sewing the sets together. That is the tricky part; when you sew one set to another, there is a need to leave a portion of the seam unsewn at the end so that you can add the next set. The edges of the quilt don't quite follow that kind of assembly, but with the main portion of the quilt assembled, that should be slightly easier to handle.