I'm in Colorado, around your elevation I think. Make sure to keep it around 68-70 degrees the whole time it's rising, low 70's is ideal.

150 g starter (I usually do 50g starter + 50g water + 50g flour a day before I plan to make it)
Mix with 25g olive oil and 250g water, mix until well combined
Add 10g salt and 500g flour (preferably bread flour), mix until combined it should still be shaggy
Wait 30-60 minutes (60 is better than 30), form it into a smooth ball
Wait 1 hour, stretch and fold (pull up part, wiggle and stretch it a bit, fold it on top. Rotate 90 degrees, repeat until you've done 4 total)
Do it again after another hour or so, I usually do it 3 times total
After around 8 hours after adding the flour and such, form a boule and place it in Dutch oven with parchment paper and flour (keeps it from sticking to Dutch oven)
Heat oven to 450, leave it for around an hour or so
After an hour, put flour on the bread, spray it lightly with water if you can. It should be kind of fluffy/bouncy. Make a cut with a razor or sharp knife
Reduce the oven to 400 and put it in the oven (with the lid on the Dutch oven)
Bake for 20 mins with the lid on, remove the lid and bake for another 40-50 minutes
Remove from the oven and take it out of the crockpot, put it on a cooling rack
Don't cut it for at least an hour to let it finish baking