Preheat the oven to 400 degrees and line a rimmed baking sheet with parchment paper. Place the saltines on the sheet in a single layer.
In a medium saucepan over medium-high, melt butter and brown sugar together and bring to a boil. Stir occasionally until combined and sugar is melted. Continue boiling, undisturbed for 5 minutes. Remove from heat and pour caramel mixture over the cracker layer. Spread out with a spatula to cover the saltines evenly.
Transfer the sheet to the oven and bake for 5-6 minutes, or until just bubbly.
Remove the sheet from the oven and sprinkle immediately with chocolate chips. Return to the oven for 2 minutes, or until the chocolate begins to melt and becomes shiny. Remove from the oven and spread the chocolate out with an icing spatula. Immediately sprinkle with the pecans and salt.
Transfer the sheet to the freezer until the chocolate is firm, about 30 minutes. Break into pieces and store in an airtight container in the fridge for up to 1 week or in the freezer for up to 3 months (see more below!).