By the way, if you want to make craft items that require synergy, and don't want to skill Synergy to be able to craft them, you can do it with 2+ people without Synergy skill. My friend's skill was 0 and mine was 14.
Recommendation: Before starting, buy a stack of Kitron Macrarons and pop them before working with the machine. There's no reason why you shouldn't maximize your skill gain while beating the system.
How I Did This for a Fisherman's Stall:
1.) Trade appropriate materials to the furnace.
2.) Have 1+ friends navigate to Water Fewell in the menu, and feed fewell (You should do the same).
3.) Spam "Enter" on your keyboards as fast as possible, stopping when you hit the element mark (the cursor will stay on water every time, unless the furnace explodes).
3a.) If the furnace explodes, you will have to navigate to "Feed Fewell" >> "Water" once again. Repeat the spam.
4.) (Conditional/Ideal) When you hit the 99 Water mark and if the furnace still has 5-10% HP, everyone should stop feeding water fewell, and feed other elements to pull them out of the negatives.
5.) End synthesis before the 5% mark. If the furnace is sparkling, you should end the synthesis and will have a chance of a successful synthesis.
Note: The furnace will blow up a few times each attempt, please do this with a 99 job so you don't die. Zone into a Mog House to save time on healing.
I did this for both the Fisherman's Stall and Fisherman's Smock. It only took us 4 attempts to succeed with the stall, and 5 attempts for the smock (different friend, still 0 skill). The Fisherman's Smock (and other multiple element items) are a little more difficult, considering that Ice needs to be raised along with water.
The strategy for a Fisherman's Smock is to have one person focus on Ice and the other on Water. The least experienced person in the party should just focus on Water (main element) and stop when the 83 mark is hit. The person responsible for Ice should spam Ice until ~40 (this number will go down later, since Fire will be fed at the end to pull it back to zero), then focus on feeding other elements that will find their way into the negatives due to the elemental circle relationship (typically only Fire and Wind). Finally, polish off the elements to be as close to their ideal levels as possible, and end the synthesis.
I personally hate Synergy due to it's necessity for these items. Take the spam shortcut. It's really fun, and you'll probably laugh at the end because you just beat the system and saved yourself 10+ hours (and tons of gil) grinding for skills.
Repeat this process for other craft stalls. Spread the word.
Godspeed,
Videob