There are many ways to make quills and inkpots, but here is how Emily made hers for her Harry Potter party.
Our quills were essentially the ink reservoir of a ball point pen shoved into the shaft of a turkey feather.
These are the turkey feathers we used. We got ours from Michaels. You can buy black-only and white-only packs of three, too; ours was a five pack of colors.
Here is the ball-point pen we harvested for ink reservoirs. This was a $1 party favor we bought at Party City, very similar to this. The ink tubes come off easily with a pull.
Emily cut off the tip of the feather shaft
and pushed the ink tube into it, making sure to leave the tip protruding.
She also used a dab of hot glue to secure the ink tube in place, so that it wouldn't slip back into the feather shaft when the quill pen is in use.
She made a whole batch of quills this way.
For the ink pots, she considered several options, including simply drilling a hole into a block of wood. She finally decided on this stack design, made from wooden wheels we had in our wood blanks stash. It's cute and very stable. You can get these wooden wheels in craft stores like Michaels and Hobby Lobby.
The round bead in the top tier is a ball of black polymer clay. Round wooden beads, if you can get them with a large enough bore to accommodate the tip of the quill, are another alternative, but we didn't have those.
So Emily improvised with clay like this and made holes to size. Don't they look dangerously like olives? If you make these and have little kids around the house, be careful where you leave them!
She then assembled the stacks with hot glue and painted them black (not necessarily in that order).
Each guest got to buy their own quill and inkpot in Diagon Alley on the day of the party.