Can anyone tell me how to craft the coffin, I have all the mats.

But i can never seem to complete before running out of durability.

I have spammed Basic Synth with Master Mend II and it doesn't work.

I have tried Ingenuity II and spammed Standard Synth.

I have used food buffs and FC buffs and even the carpenters table with no luck.

My Craftmanship is 763 and Control 737 unbuffed. What am i doing wrong ?