Preheat oven to 350 degrees.
Combine the flour, sourdough starter, softened butter, and seasoning until dough comes together and is smooth. I prefer to kneed by hand.
Divide dough in 1/2. Shape into 2 round discs, wrap separately in cling wrap and refrigerate for 45 minutes until dough is cool and firm.
On a piece of parchment paper, roll one disc of dough until it's about 1/16" thick. NOTE: the dough will have uneven edges as you roll. It's ok and it will still taste amazing!
Slide the parchment paper (without moving dough) onto a baking sheet. Then, using a rolling pizza wheel, cut the dough into small squares (about 1-1.5").
Lightly coat the crackers with olive oil using a brush, then sprinkle sea salt over the top.
Bake until slightly golden brown about 25 minutes, turning the baking sheet half way through cooking.
Allow to cool and then enjoy!
To store, you can simply use a ziplock bag and crackers will keep up to one week (but I bet they won't last that long!).
NOTE: If you prefer an herb cracker vs. everything, replace it for 2 tbsp of seasoning of your choice but also add 2 tsp of salt to your dough on the initial mix.