In a large bowl, stir together the starter, flour, oli/butter and salt. Mix until a dough forms, bringing it together with your hands. Knead it a few times until smooth and then wrap it in plastic wrap. Refrigerate for at least 30 minutes.
Preheat the oven to 350 degrees F. Line a baking sheet (or 2) with parchment paper.
At this point I separate the cracker dough into two sections - it’s easier to work with this way. Take one piece and place it on a floured workspace. Roll it as thin as you can - the thinner the better, without tearing - like ⅛ inch or thinner. Gently transfer the dough to the parchment paper (or you can actually roll it out on the parchment and transfer the parchment to the sheet!). Brush the top of the dough with olive oil or melted butter. Sprinkle the BBQ seasoning mixture all over the top. If you’re making plain crackers, sprinkle with flaked sea salt.
Bake the crackers for 10 minutes, then rotate the pan and bake for 10 minutes more, or until golden and crisp.
Let the crackers cool completely before breaking them into pieces. I store these in a resealable bag for a few days. Though the rarely last because we eat them all!