Mass Production Achievement, Quick and Easy.

[Deku Scrub]

Well, the create 100 things using an assembly device is pretty easy with the Insta-Mash Potatos.
All you need is 3 Tatos (which are readily avaliable if you've been stocking them for Vegetable Starch) And 1 Cloth (which you can easily get with Pre-War Money (if you don't have 100+ Pre-War Money, there's a bank in Lexington near Super Duper Mart.)
So, as I'm typing this I have 2-3 assemply line producers churning out a massive pile of boxed mash potatoes in Sanctuary.
Figured I'd leave a tip if anyone else wants an easy way to cheese this achievement and get back to playing their gloriously modded version of Fallout 4.