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if i remember well you can sit if your lvl is at least 15 lvl or so below the lvl of the recipe.
This is probably true. I have used this technique to test out two hour macroes to make sure they are working correctly. By kneeling and engaging /heal mode I can hit my 2hour macro and if it's broken fix it. If it is working correctly I basically get an error message to the extent "This action cannot be performed while healing", telling me it works. A very useful trick for those weird spelled 2hours that you need to work right.
There is actually an easier way to do it though. This used to be a leveling exploit that was long since patched if my memory serves, but its still useful for getting level cap information.
If you go outside a starter city such as gustaburg and engage a worm, but stay very far away so as to not hit the worm you will be in auto attack mode and still able to try and craft your item. However due to being in engaged mode should you be of proper level you get the message "Synthesis failed, you lost the crystal you were using". The crafting materials will however not be lost. I have tested this personally on my goldsmith in gustaburg. I brought a copper ingot and a wind crystal to gusta south and engaged a worm from afar. I then went to inventory and used the wind crystal on the copper ingot. The message said my crystal was lost, which it was, but my copper ingot was retained, and the copper hairpin synth never even attempted.
It still holds true to the 15 levels below cap requirement to synth however. My goldsmiths cooking skill is zero, so I bought ingredients for one insect paste synth, and went and ran the same test. I got the message "that synthesis recipie is beyond your current skill", so it never attempted and I still retained the earth crystal as well as materials.
Using this method one could test out sub craft levels without ever running risk of losing anything extremely valuable. As long as you never go near the mob enough to hit it or get hit you will be immune to material loss. This method is in fact how Mikesjustice found out the crafting sub of haubergeon and thus confirmed it is currently impossible to breach tier 2 without ever running the risk of losing the D ingot.
NOTE: The reason this only used to be an exploit is because you used to be able to actually get skillups doing this. From what I'm told s-e shut down the servers for emergency maintinence within hours of the trick being discovered and now you can spam this forever and never get a skillup. All you will ever do is waste crystals on nothing. So it's only use is finding subcraft levels, which one could potentially do anyway, they would just have a critical failure when it went through and lose everything.