Gather a few tools -- 2 pins, a 1/4" wide ruler, a 2.5" square ruler, and maybe a wooden presser to help give you nice sharp edges. If you have a Cathedral window template ruler, it can help you see the pattern on your fabric that you want in your window.
Fold your piece of fabric in 1/4" on all 4 sides. I use the 1/4" ruler to help me with measuring the edges and to press the fabric. You can use the wooden presser or your finger also to make the edges sharp. Try to make all four sides a consistent measurement. As long as all four sides are the same, your block should fold correctly.Next, fold each corner of the fabric into the middle,
again pressing with your hand or the ruler edge. 
Try to make sure the points meet in the middle and are even. It might help you to mark the center with a pencil dot. Your goal here is to make sure the outside four corners meet in a sharp point. Don't obsess over it though. They don't have to be perfect to work.The next part is kind of tricky, as you have to hold the four pieces with one hand, while you're folding again with the other hand. I use the ruler to hold 2 sides down while I'm doing this. Again, fold the 4 edges to the middle. The closer your points meet, the nicer your block will turn out. That is why a slightly stiffer material is helpful.
Pin the two opposite sides, then pin again. Press the outside edges with your finger or wooden presser. Set this aside and fold two more blocks.Going back to block one, sew the opposite sides that you pinned (using just one or two threads), then sew the remaining two edges (opposite one another) you have pinned without cutting the thread. Knot this thread and tie it off. Do the same with blocks two and three. Lightly press the blocks flat, so your edges are nice and crisp.
Take two of the blocks with the solid backs together and whipstitch the edges. Make sure you hide your knot on the inside of the folds, you don't want it to show on the back. I have tried the whipstitch many ways, from a tight stitch to a wider stitch. The wider stitch seems to work just fine, takes less time, and will be hidden when you place fabric over it. When you finish these two blocks, whipstitch the third block to the second block.Choose 2 complementary fabrics, perhaps one with teapots, or gardening tools, and a flower pattern that accents the first fabric. Cut eight 2-1/2" squares from the flower fabric and two 2-1/2" squares from the teapot or garden fabric. Fold all the flower fabric squares in half and press. Leave the other two full size. Lay the fabric on top of your sewn cathedral window blocks, with the folded edge to the outside of the piece. Fold the edges of the fabric over your 2 1/2" square and use a blind stitch to hold the fabric in place.
Do not sew through to the back of your square. To finish, sew a piece of lace about 1 yard long to the front of the piece (these threads will show on the back) and attach little buttons or pins to decorate. Buy a decorative hanger and sew it to the top of your piece. You have a lovely gift and you've learned how to make a Cathedral Window. You can use the same technique to expand your window project and
make it a quilt.
