Line baking sheet with sides or jelly roll pan with parchment paper or aluminum foil (or our favorite, a silpat liner). Spray parchment or aluminum with cooking spray.
Line parchment with a single layer of saltine crackers, sides touching, to cover entire bottom of baking sheet. You might need to break a few to get them to fill the spaces.
In a medium-sized sauce pan, you’ll melt butter and brown sugar over medium heat until bubbly. Stir with a whisk and let boil on medium for 3 minutes.
Pour the caramel mixture directly onto the saltine crackers in the baking sheet. Spread the mixture over the top of all the crackers with a spatula or the back of a spoon.