Add the starter, seasoning, and salt (if using). Stir well with a spatula.
Line a baking sheet w/parchment paper (MUST be parchment – do not use a silpat mat).
Pour starter onto the parchment paper using a spatula. Spread into a thin layer making at least 12″x 9″ rectangle.
Bake 10 min; score with sharp knife using an up-down motion – not a pulling motion (that tears the cracker).
Bake 15-25 more minutes, checking crackers at 15 min and then every 5 min after to ensure browning but not burning. Rotate the pan if one side gets more brown than the other.
Cool on pan for 5 minutes, then store crackers in glass container w/lid – if they last that long!