When I was starting to plant the first sempervivums and jovibarbas this year, I browsed the Internet for the best methods to do so and often found the hint to give the soil mix a good coverage with fine gravel after having finished planting to allow for good surface drainage and prevent the plants from getting too wet from below.
Following this advice. I planted my sempervivums in a mix of sand, gravel, and some peat-free potting soil, with an underlayer of gravel in the shallow plates I had prepared, and tried to apply fine gravel (3-7 mm/ about 1/4- 3/8") ... and finally ended up poking gravel out of the tiny rosettes of my plants I hadn't intended to harm that much. This took me longer than the actual planting. Furthermore, the gravel was distributed anything but uniformly.
Obviously this method, which in Internet videos was always demonstrated on a single, freely accessible rosette, did not work for me in my rather densely planted plates. (I might have to explain that I like my sempervivums/jovibarbas to form carpets rather than dense clumps. That is why I separated and cleaned almost all of the rosettes before planting, even the arachnoideum types.)
That was when I came up with the idea to turn things around and to prepare all layers, including the gravel coverage (about 1 cm or 1/2"), before planting anything. Obviously, you cannot dig big holes in this case without mixing the cover and soil layers. That is where a wooden pick comes in handy, as it allows you to prepare a deep narrow channel in the soil, perfectly adapted to stolons or shorter roots. If bigger or longer rootstocks are to be planted, I scratch the cover layer away, place the rosette on top of the soil, and use the pick to guide the roods into the soil. Afterwards, I draw the cover layer back towards the rosette again, using the wooden pick.
This method results in rather uniform gravel coverage and you do not run the risk of erasing or covering smaller rosettes by applying gravel.
Below you can see photos I just took of some of my plates. The preparation of the plate took me 10 minutes, including the drilling of a drainage hole in the bottom of the plate. Planting took a bit longer as there were so many rosettes to plant.