During the rough out and rough shaping steps the folded corners of the cattail leaves were left at the original level of the wood. This gives lots of room under the fold to create a free-floating leaf.
Begin by marking a v-shape on the side of the front leaf, just under the leaf fold. Mark the top of the leaf at the fold with the v-shape. Note that on both areas that the tip of the leave where it touches the background will not be free-floating, only the fold area will be worked. this gives your leave an anchor point to the wood, making it stronger.
Note: During any carving session I stop about every half hour to strop my tools. It brightens the edge while giving me a moment to think where I am going to work next. Before you begin these free-floating cuts take a moment to freshen the cutting edges of your bench knife, chisel, and large round gouge. A well sharpened knife puts less pressure on a cut than a dull one.
Working the upper side of the leaf, with your chip carving knife or bench knife make a thin slice along the pencil line, slanting the knife tip towards the background. Make several passes at this cut, slowly and gently deepening the cut.
With your large round gouge, straight chisel, or bull nose chisel make a cut into the v-area with your tool’s cutting edge as low onto the background as comfortable. As you work you will release small, thin slivers of wood from under the leaf fold.
Repeat the free-floating steps for the underside of the leaf fold.
Once both sides of the leaf have been undercut, using your large round gouge or wide sweep gouge begin lowering the background level under the leaf fold. Merge this drop in level with the surrounding background by making a few, long, but shallow gouge cuts towards the leaf area.
For me, I find that making a few undercuts followed by a few background gouge cuts I have more control over opening the space under a free-floating element. So I work these steps in increments. Your basswood is stronger that you may realize and can take quite a bit of pressure, but slow and sure avoids any cracks or breaks in the free-floated element.
If you do break or crack an area, gently open the crack with a little prying pressure from below and use a few drops of super glue! Remove the pressure and let the glue dry for five minutes, then go back to carving.
To clean up the underside of the free-floating area I fold a piece of 220-grit sandpaper and slide the paper through the opening. Sanding will also help to widen the corners of the free-float.