Sand area with 80 grit sandpaper.

Wipe down with damp cloth, sponge, or paper towel.

Be careful to not wet down the patch with too much water. Only minimum amount of dampness needed to wipe away sanding dust.

Apply thinner coat of joint compound with a 6, or 8 inch putty knife.

Pay attention to put pressure on the outside edge.

Let dry for 2 hours.