I can't remember the name of the technique, but what I do is put the potting mix in , then an inch(there abouts) layer of grit, then the cutting, then more grit on the sides of the cutting to hold it in place. Water as usual. The cutting senses the moist mix below, but isn't sitting in it, so it sends out roots to the moisture. The grit drys out, so it doesn't rot the cutting. Works for rooting easily rottable cuttings.
My mom accidentally used that technique to root a saguaro. Her's rotted, so she cut the top half off, that wasn't rotted, and placed it on some gravel in her garden. Threw out the bottom part and never got around to throwing out the top part. It rooted in place. She had been told that you couldn't root saguaros.
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