I made a 2-1/2" patchwork heart block. The pieces each measure 1/2".
Here is the thumbnail draft.
Next I laid out 1-1/2" fabric squares on gridded fusible interfacing. It's so much bigger than the finished block because I sew half inch seams and trim to 1/4". For full instructions visit this post.
I didn't take a picture of the next step, but using a craft knife and a ruler I cut a window in the card. The picture above shows the block from the inside. After it's in position I used double-sided tape to hold it in place.
Then I covered the block with plain paper for a finished look.