Preheat the oven to 350℉ and line a baking sheet with parchment paper.
Melt the butter in a large measuring cup or mixing bowl and let it cool until just lukewarm.
Measure in the sourdough discard and salt, and stir together with a spatula until well combined.
Add cheese and stir until well incorporated.
Pour the mixture onto your parchment-lined baking sheet and use an offset spatula to spread it into a thin, even layer that is almost transparent.
Lightly sprinkle the top with flaky salt - don't overseason.
Bake for 10 minutes then remove from the oven and use a pizza cutter to score your crackers into bite-size squares.
Return to the oven and bake another 20 minutes or until the crackers are golden and hardened.
Remove from the oven and let cool on the baking sheet to let them fully dry out.
Once they have cooled completely, store in an airtight container or zip bag.
