The bamboo pocket of bonsai should be young and energetic. Dig as many roots as possible. After digging, the original bamboo pocket growing horizontally will be rotated 90 degrees to stand up for planting, but in order to make it survive, the whole bamboo pocket must be buried in the soil and buried into a small mound. After the bamboo survives, with the wind and rain, the soil on the mound gradually falls off until all the bamboo roots are exposed. At this time, you can take out the bamboo bag and put it on the basin for pruning.
In fact, the process is still very long. I've seen others do this. You'd better find a picture or do it with others several times. I don't think bonsai is like other techniques. Just learn the process. Sometimes you can do everything, but you can't live. We need to practice a few more times. I hope I can give you some ideas.