I-5

This one was a bit of a head scratcher but in the end was really simple.
Just applique.

Print or trace the block diagram onto freezer paper and cut out the outside "frame".
I cut out the melons too since I use freezer paper for applique.

Cut a 6"x6" piece of your main block fabric and iron the freezer paper down on the right side of it.

Using the freezer paper as a guide, applique the four melons onto the main fabric square.
PLEASE NOTE! The melons are not symmetrical. Make sure you attach them the right way round. The less rounded side goes toward the center of the block.
I appliqued the sharp ends of each melon first and then "filled in" the rest.

Carefully remove the freezer paper frame or print/trace another one.
Cut a 6"x6" piece of background fabric and iron the freezer paper frame onto the right side of the fabric.
Cut out along the inner edges of the frame, leaving a seam allowance. Clip into the seam allowance almost to the freezer paper edge every 1/4" or so.

Place the main fabric square right side up on the table. Place the background fabric "frame" right side up on top of it. Baste through all layers to keep them from moving. Don't baste too close to the freezer paper edge because you'll want to turn under the seam allowance.

Turning under the seam allowance, reverse applique the frame to the block.
Trim the block to 5"x5". If you leave the freezer paper on, you can trim 1/4" beyond the freezer paper edge on all sides and your applique will be nice and centered.