Niffelheim

This will most likely happen naturally as you go for the Platinum, because you'll need to craft a lot of items at the Alchemy Station just to upgrade all of your buildings and workstations, not too mention crafting all of the Potions you’ll be using to defeat the Bosses.

The Alchemy Station is one of four workstations you'll build inside your keep (it's the station furthest to the right). You'll be knocking out a good chunk of the 100 with Flammable Tar and Beer as these are the basic materials needed to craft better quality Potions and Brews. You always want to make sure you have Potions (Health, Strength and Defense) on you as you go adventuring and each of those will require you to craft 2-4 Alchemy items each, which will greatly increase your count to 100.

If you somehow don't have this trophy by the time you reach 100 days played for Hermit, collect Twigs and Resin (both collected from cutting down trees) and keep making Flammable Tar until you reach 100 items crafted. Once the 100th Alchemy item is done, the trophy will unlock.