I’ve had pretty good success the past few years making Eric’s Artisan sourdough rye that comes out as good as the best pictures show and is quite a hit here when I bring to friends etc. Trouble is I am tired of it. Am trying now to make a more Ciabatta style ( 5 flat ugly ones so far)…with white and spelt and not getting it. 2nd rise produces a bubbly very sticky dough, well risen, which I thought was a good sign…but it always ends up pancake style after putting it in the round clay baker. I see many picts on-line of very open crumb “ciabatta style” round loafs…which I can’t seem to get. Any ideas? Thanks
I guess many, if not all, of these perfect examples of ciabatta are made from bread flour and the majority are yeasted breads. Yours being a sourdough with spelt might have something to do with the differing results.
Not that it can’t be done but do expect them not to be identical and you might need to have a slightly different approach.
My best advice would be to keep it simple till you nail it and only then experiment further.
Total guess based on your description of a bubbly, well-risen dough, but try reducing the time of your bulk and/or 2nd proofing. If you let it over-proof, then by the time you get it into the oven it can deflate.
3rd baker, 3rd opinion 
I’ve been making bread for 40 something years and sourdough for almost 5 … Ciabatta is my nemesis!! I get nice air holes but my bread/rolls RISE up vs staying slipper like and I’ve not had much luck getting a crispy crust.
However, my best success has been with the Spelt Ciabatta on this site and with “the perfect loaf” ciabatta. I am mystified as I cannot see a lot of difference between “the perfect loaf ciabatta recipe” and this site’s “white flour” ciabatta. AND, I tend toward “recipe as guideline” … still … above is my personal experience.
The other thing … I bought a stand mixer for the express purpose of making ciabatta having watched many, many youtube videos on making ciabatta. And I do mix ciabatta with the mixer … to the point where the dough is “whap - whap - whapping” and all gathered around the dough hook. Additionally, I found that when I paid attention to shaping, my results were best.
Take above FWIW and “with a grain of salt” … just what has given me the best results … except for the VERY crisp crust 