Keep in mind:
The danger of a timeless plane is that once an individual leaves such a plane for one where time flows normally, conditions such as hunger and aging occur retroactively.
Actually, a timeless plane just stops you from aging while you are there -- and there are much safer ways to slow down or halt your aging process.
For crafting purposes, the best you can do is create a demiplane with the Flowing Time trait where time flows twice as fast for you as it does outside of the demiplane -- then you can get double the amount of crafting done in half the (outside) time.
Greater Create DemiplaneBut it only has a duration of 1 day/CL, so would that mean I could only stay in the demiplane for a maximum of 17 days?
The spell description gives information on how to make the spell permanent.
The first question to ask is how your GM interprets the interaction of Timeless Demiplanes and the duration of the Time Stop Spell.
Ive argued against the infinite time interpretation because of the inclusion of the term 'apparent' next to all occurences of the duration... That said, I've seen plenty of arguments for the opposite interpretation as well.
Another possible method requires mythic rules to be in play. I'll leave that out unless it's a thing somebody is interested in.
Pretty much any way you can come up with to do this, however, is going against the fairly clear intent of the developers (as displayed in the restriction on Flowing Time in the demiplane spell)