What is the Flamenco Tientos?
The flamenco Tientos is often danced, and is generally slower than other Tangos. However every Tientos does speed up and become a tango by the end following the dance escobilla sections.
The Tientos four beat compás can be counted with accents on beats 2 and 4. The Tientos compás can be a bit tricky to notate and get the feel for, and will sometimes appear as a combined 2/4, 6/8 time signature.
There is a distinctive syncopation in the rhythm, one of the simplest variations can be seen here:

Flamenco Tientos Examples and Links
Here are some of my favorite Tientos examples: