In a large mixing bowl, put in the sourdough starter, water, instant yeast, and sugar. Stir together and let sit for a few minutes.
Add 4 c. flour, instant ClearJel, and salt.
PROOF
Cover bowl with towel or beeswax wrap and put in a warm place until it doubles in size (about 1 1/2 -2 2 hours).
KNEAD
Place dough onto a board or counter dusted with flour and knead by hand about 5 minutes. Add in an additional 1 to 1 1/2 c. more flour until it is smooth.
SECOND PROOF
Dust the banneton with flour and place smooth side down into the banneton basket. Cover with beeswax cover or towel.
Let rise in a warm place another 45 minutes-1 hour. The loaf is ready when it reaches slightly above the top of the banneton basket or by pushing finger into the center of loaf and it bounces back quickly.
BAKE
Turn out of basket onto a piece of parchment paper to fit a dutch oven. Place in dutch oven, spread with flour and score design on top using a bread lame.
Bake at 400° for 20 minutes. Remove lid from the dutch oven. Reduce oven to 375° and bake an additional 25-30 minutes until center is 205°.
Place a baking pan with some water on the bottom of oven. This will create steam during the baking process.
Let bread cool before slicing. Cover and store in airtight container and keep on counter 1-2 days.