It takes a while to develop callus at/below soil level on cuttings. Burying a cutting too deep will greatly increase the risk of rot especially in richer soil blends. If you have a tall and heavy cutting however, you will need to bury deep enough to provide stability. One technique is to fill the pot slightly more than 3/4 with your soil blend, then position the cutting and backfill around the plant with an extra thick, non-organic top dressing layer for the top few inches to provide stability and facilitate callusing. Another technique is to just pot the cutting at the required depth for stability in a VERY well draining substrate blend containing only one quarter part organic matter and water more frequently once rooted. Either way, the plant should be repotted within a year or 2 depending on the size into an ideal substrate and container for that plant. Experiment and try new ways, there's no wrong way to do it as long as it works for you 😉
It's very important to allow the cut end of the cactus to callus over. This creates a protective barrier that helps prevent moisture from entering the plant, reducing the risk of rot. We suggest taking the plant out to inspect it, cut it again if there is any damage or soft/dark brown spots, and let it callus properly before replanting. Hope this helps!