Drain the thawed spinach in a colander set over a bowl. Use a paper towel to press out the excess liquid. Add the spinach to a medium sized bowl.

Drain the artichoke hearts and chop them into bite-size pieces. Add the artichokes into the bowl with the spinach.

Next, add the cream cheese, sour cream, salt, pepper, and garlic powder to the spinach bowl. Stir to combine the ingredients slightly.

Lightly spray the inside of a 2-quart Crockpot with nonstick cooking spray. Add the spinach artichoke mixture to the slow cooker.

Cook on low heat for 2-3 hours, stirring halfway through to prevent burning around the outside of the dip.

Once the mixture is bubbling and creamy, turn the slow cooker setting to "warm" and add in the cheddar and Swiss cheeses.

Stir the dip until the shredded cheese is fully melted and creamy. Give the dip a taste and add more salt or pepper if needed!

The dip can stay in the Crockpot on warm for up to two hours.