You can add a stem onto the base of a leaf or flower without cutting the base fabric.
Here's a block from a project that I'm working on. I put on the stem without cutting the white square.
First, make a strip of stem fabric that is longer than the square. The excess will get trimmed off. I made my stem's strip 1-1/4" wide and folded it like bias tape to make sure it was a good width. Position the strip and check it to see how it looks centered on the white square.
Place the right sides together but lay the strip off to the left of the center of the square. Stitch it down and press the strip so the right side is up and over the center of the square.
The next thing you have to do is fold the opposite edge under and press it. Now it will look narrow like a stem. Run it through the sewing machine with a thread that matches the color of the stem, stitching close to the edge. This seam will not be hidden.
Trim off the extra fabric of the ends to line up with the edge of the white square.
That's it! Easy and quick and your base square will stay in tact. Uncut and correctly sized! I have made stems with the base square cut in half and the stem pieced in. This looks just as good, in my opinion. You can even make the stem curve a little if you want it to. That's a nice effect! Give it a try - let me know how it works for you!