Say you wanted to write a tefillin, mezuzah, Torah, or any other sta"m venture. To make it easier for you, you created a stencil of the text that you can overlay on the klaf and fill in. You hope thereby to avoid mistakes and have the letters always perfect.
What are the halachic issues you may run into here? If it's OK in theory, must you fill in the letters as if the stencil weren't there (ie. follow "stroke order"), or could you simply fill the empty spaces with ink (in letter order, of course, if you're writing a tefillin/mezuzah). Are there any halachic authorities that speak to this?
I'm reminded of the silk-screen Torahs, created similarly (rolling ink over a stencil, many words at once). Comparing with the problems raised in one of the answers to that Mi Yodea question, hand-writing one letter at a time with stencils seems to avoid the issues.