See this entire project and steps on how to do it at Cordwood Construction. 
Prepare surface by sweeping and mopping clean. We are gluing directly onto our concrete slab. Sand both sides using a belt sander. Begin to layout disks on the floor. Try to get them as close as possible. Work in 2′ sections.
via Cordwood Flooring by Sunny in sunny Arizona | Cordwood Construction.
Only the tower’s top level is still a bedroom, now with reclaimed fir floors, handcrafted mahogany bed and window frames, and whimsical oak dresser. (Collin Andrew/The Register-Guard)
“But what I like to do with all of those things, is try to select out the stuff so that it doesn’t look like a salvaged house,” Pollack ruminates. “I never wanted it to look that way. I wanted it to look like everything was selected from a top-notch building supply store … but it wasn’t.”
via The carte blanche carpenter’s house | Home & Garden | The Register-Guard | Eugene, Oregon.
The company had to carefully de-nail the beams, as well as chop back the parts that had extensive rot caused by long-term water leaks in the building. The company was able to manufacture the salvaged wood into six grades of flooring.
via Company Cuts Back Rot to Salvage Boards From Leaky 1920s Building – Hardwood Floors Magazine.