Basically, long time fermentation and low temperature fermentation will grant big holes to your dough. However, high hydration doughs will have bigger holes than others. Also you can fold and stretch you dough if you wish, but the dough should not be completely degassed, so you can get big big big holes. Also you can incorporate air to the dough while kneading.

Esteban.

I am developing a recipe (boule) that includes these instructions (and they work) for the relatively wet dough I make.

With lightly floured hands, turn dough out onto a lightly floured surface and separate into two pieces of equal size.  Shape the dough gently into somewhat square shape.  You  may find it necessary to "re-flour" your hands periodically to handle the dough.

Avoid deflalting the dough and stretch each square piece, in turn, away from your body to elongate it into a rectangle.  Fold the long end of the dough back toward  you, turn the dough 90 degrees and repeat this procedure three more times.

To complete the forming of the dough into two loaves, gently pull the surface tension taught by using both hands to rotate the dough and, with one hand, simultaneously stretch the dough by pressing the lower edge under the forming dough ball.

Place both loaves on peel covered with lightly floured parchment paper.  Lightly dust top of each loaf with flour, cover with towel or plastic wrap and let rise until nearly doubled, about 40 minutes.

Preheat oven to 500 degrees (I use a pan of boiling water on the bottom rack to provide some steam).

Place raised loaves on baking stone in the preheated oven, bake at 500 degrees for 5 - 8 minutes, then lower the heat to 450 degrees.  Bake to 205 degrees internal temperature and remove from oven to cooling rack.

I am very new to bread baking so this is not expert advice.  It's just a description of what works very well for me at this point in time.

Thanks for your suggestions on how to get big holes in your sourdough bread.

I will try your suggestions.

ur not gona get huge holes from sourdough bread if ur only using the natural yeast beacause it works alot differently than the stuff u can buy in a packet. Obtaining a satisfactory rise from sourdough is more difficult than with packaged yeast, because the lactobacteria almost always outnumber the yeasts by a factor of between 100 and 1000, and the acidity of the bacteria inhibit the yeasts' gas production. The acidic conditions, along with the fact that the bacteria also produce enzymes which break down proteins, result in weaker gluten, and a denser finished product.

Higher hydration is one means of getting the big voids but also I find that working the dough less helps, too.  Instead of doing 3 French folds I only do one or two.  Also I autolyse for 30-40 minutes and knead for only 10 seconds, adding my salt last.

This link, which includes both helpful information in the form of text as well as fifteen minutes of instruction by D. Reinhart, may be of some value:  http://www.finecooking.com/item/9929/sunken-sourdough-sadness#