As you'll note, there is a wide range in the amount of flour needed. The essence of ciabatta is it's coarse texture with large interior holes; this is possible with the right proportion of flour and liquid. A dough with too much flour will have a fine texture; a slack dough, one with too much liquid, will spread out on the baking sheet, rather than rising up. Experience, and maybe a few failures, will teach you just what the dough of a perfect ciabatta should feel like. Found this recipe on King Arthur's website.