1. Make a list of the 30 things you would want to wake up in the middle of the night, reach over with eyes still closed, and accidentally put your hand in. It shouldn't be there, there's nothing on your nightstand except your phone, what's there? Why is it there? What is happening to you? Why are? Animal oo-oo-aa-aa reactions. Gut reactions, visceral grossout reactions. Build a dungeon that can only be navigated by blind touch, and include as many of those textures as possible.
2. Make a list of magic words that can cast common spells compiled from some horrible internet listicle about words people find the most discomforting. Panties. Phlegm. Moist.
3. Take any monster with a spine. Remove all bones and squeeze it to a shape consistent with a bean bag chair. Its only means of locomotion is someone being terrified of it and chases the player most obviously squicked out by this. Always somewhat warm.
4. Make a loop of Plant's scream from Immigrant Song. Play it when a giant shows up, on constant loop every time a giant goes each round.
5. Dream of drowning.