If you have decided to “make” your own Seal Stone, then you will need to determine which kanji to utilize (if your not “Japanese” to begin with). It will be necessary to “sound out” your name “phonetically”, into as many syllables as are needed. It should be remembered, that the “idea” is to make it legible to a Japanese individual. If your name utilizes sounds unfamiliar to them, they won't understand how it's supposed to be pronounced. There are commonly accepted “sounds” which the Japanese utilize when these unfamiliar sounds are encountered.
Of these, the ones most common to cause difficulty, are the “L” sound (usually substituted with an “R” sound), and the “V” sound (usually substituted with a “B” sound. It sounds a little “racist”, but if one imagines a (bad) movie (where someone is trying to “sound Japanese/Chinese”) you will actually get very close to how a Japanese person might pronounce those sounds.
Once you have broken your name down to syllables, search through the provided lists(well, for “my” students, LOL), or dictionary's to find the individual sounds represented by the kanji. There are (usually) numerous choices of each. On “rare” occasions, you might locate words which “match”, or are very close to the name/sounds given.
It becomes a time consuming process, but if one investigates the meanings behind each “match”, one can (usually) find a string of equivalent sounds, with “meanings” that will be acceptable for use. But, if your going to the trouble to make a seal, you might as well make one that has “some” sort of legible meaning. Understand, that it is NOT the meaning which is important, it's the SOUND (of the kanji being used). What one “usually” winds up with, are a grouping of words/meanings that are assembled similar to a “haiku” or “poem”(without the usual “particles” of speech that would commonly be utilized when writing).
For a name, or organization’s seal, it is common to utilize the “Tensho” (“seal”) style of writing(“font”?). For any other type of seal, it's the individual's choice.
When making a seal stone for one's name, the kanji is carved “into” the stone. If you are doing a “pen-name”, those are usually carved in relief (you carve away all but the kanji). Either method is acceptable for “other” types of uses, though many “businesses/organizations” will often use the 2nd method for representative “stamps”.
Once one has determined “what” to put upon their seal, you then have to carve it. The straight “name seal” isn't too bad. It's just a matter of “reversing” the kanji (simply done on a computer within most graphics programs) and print out a copy (for reference).
The next step is to transfer the image onto the stamp itself. This is usually done “freehand”(using your “reversed” and printed out copy for reference).
There are traditional “chisel's” of varying sizes (which make the carving easier), but they do require practice to use effectively. I've found that “if” one is careful(and has one) a “Dremel” tool, with a very small “bit”, will work quite well. The most challenging task, is making sure one chisel's “deep”(enough) into the stone, for the resultant “image” to transfer when “inked”(simply “scratching the surface will rarely work).
Once one begins one of these “projects”, you will understand why person's will charge (quite a bit) for doing them(by “hand”). If/when you make a “mistake”, you get to start over,...”completely”. You must sand the entire surface “smooth” (again) before “restarting”. A number of places are available to “carve” you a stone “on-line”. Most will utilize engraving machines (which can do a remarkable job). But depending on your attitude about it, they have the/that “mechanically” made “Look”(to them). The one's done by hand are extremely difficult to reproduce (exactly as done). The machine made one's, are easily reproduced, which would be fine if one uses it for a “business” purpose. For a personal “name seal” though, “I” prefer the hand carved one's.