Homestead Arcana

The Autumn Havest Festival is an optional objective that will appear quite early in the game. It has four stages. TLDR: simply complete each of the tasks by sending the required items and, once the last one is done, the achievement will unlock.

To send items for an objective, interact with the roost at the base of the steps up to Abrahams platform. Then interact with the triangular section at the top to bring up a list of your current objectives. Find the one you want and you can send some or all of the items if they are in your inventory. Typically you will need to wait another day or so until a reply comes back. On collecting the reply, the objective will progress and/or the achievement will unlock.

I didn't keep track as I went, but according to the wiki here (with thanks to the original creator), the objectives are:

Stage 1:

• 40 x wood

• 20 x metal

• 15 x stalk

• 20 x birch

Stage 2:

• 3 x hush puppies

• 3 x caramel apple

• 2 x apple cider

• 2 x apple sauce

Stage 3:

• 3 x pumpkin pies

• 3 x apple pies

Stage 4:

• 1 x phantom spell potion

• 1 x shadow spell potion

• 1 x gray spell potion

I'd left this until the end and I'd already unlocked the Money Bags achievement, which was probably a mistake as completing this objective rewards 3000 coins, along with 3 Milk.

I think you will need to have progressed into, if not cleared, the Forest region to be able to complete all the stages. Most items are easy to find, but the Hush Puppies recipe took me a while.

*Be cautious with the destroyable walls. There is a finite amount of Sulfur and there are some necessary items behind some of the walls that are required for this and other achievements (eg. mask upgrades and spell slots). I didn't check but it might be possible to run out of sulfur without getting everything you need.
You can always make a save before you destroy the wall (turn off autosave but remember to put it back on afterwards). If there is nothing useful, exit and reload to before you destroyed the wall, with your explosive powder intact.