The video below shows the technique pretty quickly, and the link below shares a tutorial on how to use the burnt plywood to make a lovely table! If you plan to use this as flooring, it will make sense (at least as far as interior design concepts are concerned!) to cut the wood down into planks and then burn them.
NOTE, however, that the man in the video below is using a very wide blowtorch flame. It seems to be a much easier process than the one described by the woman in the blog below. She used your run-of-the-mill blow torch flame that may be too narrow to provide even burning. Sounds like she had a hard time with technique.
Either way, the effect is super cool AND cheap!