Here is another option that has worked for me on Larches, Cedar, Malus, Mulberry,and Japanese maples....
First off, your cut should be at least as wide as the trunk is thick. Use a utility knife and cut into the wood as deeply as you can with one steady cut around the trunk and then repeat below it at at least the same distance as the thickness of the trunk. In example your cuts would be at least two inches apart on a trunk that is two inches wide.
Once your two cuts are made use the blade of the utility knife to scrape the bark off, first down to the bottom cut and then up to the top cut, you will have just hard wood below this cut. The top and bottom of this cut now should be perfect, no ragged edges, and straight as can be.
Now take a hand wipe, the kind they give you with your buffalo wings with alcohol in it, and wipe the cut, this kills any remaining cells (Avoid the top cut). Wait for a few minutes...
Apply your rooting hormone to the top cut and then follow the above advice for plastic or use a plastic nursery pot....cut down the side of it and halfway across the bottom, making a small circle in the center of the bottom, big enough to fit around the trunk. Now take wire and form a base about and inch or so under the bottom cut, you can use a clamp, clothes pins, or a lower branch if it is position right.....put the pot around the tree use tape to tape the cut edge together and fill with sphagnum moss, a good soil mix, or a combination of the two.....place plastic wrap over the top after watering and this can be removed to check moisture. If you have access to deli containers, I have found these work great and the lid can be cut and place on the container as well.
In the pictures below you can see results of this method used on a Larch.
Will