palmtree bonsai

what is the mechanism used for making palmtree bonsai?

Palm Trees are monocots, that is they only have one growth point. If you damage that bud 99% of the time the plant is dead. (If you prune a palm it will die.) (You can remove dead leaves.) You can keep them in a small pot and not fertilize them much, and then they will stay small.

BUT, they are questionable as bonsai.

Three alternatives:

Sago palm (Cycas revoluta), a slow-growing, long-time acceptable specimen for bonsai.

Raphis palm (Raphis spp.), a slow-growing, somewhat long-time acceptable specimen for bonsai. Some would consider this more of an accent plant. Use the dwarf varieties.

Norfolk Island pine (Araucaria heterophylla): remove all branches except for the top ones and you have the appearance of a mini-palm tree. Some would consider the result more of an accent plant or to be used for a tropical island saikei composition. Not a true pine.

As others have pointed out, you can't make a true bonsai out of a palm tree. I have a pygmy date palm, Phoenix roebelenii, that is called a bonsai by courtesy. They even allow it in the local shows.
If you do a search on this forum, you will find where I posted it.
It meets some of the bonsai criteria. I want it to look like a date palm, Phoenix dactylifera, which grows 100 feet (30 meters) tall. The pygmy date palm grows about 10 feet tall. My palm tree has been "in training" for almost 11 years. The trunk has grown about 2 inches (about 5 cm.) and is now 5 inches tall. Unfortunately, I can't do anything about the length of the fronds, which are over a foot long, although smaller than the ones on full-sized trees in the shopping malls.
The tree is in a 7-inch pot (18 cm.). I have to repot it every year and saw off the bottom of the root ball. It is in coarse bonsai mix.
What kind of palm were you planning to use?
Iris

Sago palm isn't a palm either, it is a Cycad. One of a very interesting group of prehistoric plants that have endured.