I haven't got any CST qualifications, but I'm a big fan of their training stuff (I like the way they combine joint mobility, yoga and other conditioning bits & pieces into something that feels like whole, and some of their instructors have pretty cool movement skills).
The basic idea of a 4 x 7 is that you cycle intensity over a 4 day cycle (moderate, high, zero, low) 7 times.
There are a few different programs available for putting them together, the Sonnon one is just one example, google the bodyweight exercise revolution or check out the fitness bloggers on their forums for some other 4 x 7s aimed at particular goals. You can do joint mobility daily, yoga on the low day, with the workouts on the moderate and a high days reflecting the goal of your cycle. For a very crude example, you could do a strength session to a subjective intensity of 6-7 out of 10 on your moderate day, then a blistering metcon to a subjective intensity of 8-97 out of 10 on your high day. The idea would be you do the same* strength and metcon each time for the 28 days, and then you see some nice improvements over the month.
BTW I don't have the Sonnon product, but I do have the bodyweight one, and it seems pretty good for someone without a huge CST background (they include a basic joint mobility and yoga session attached to the e-book as .mp4s).
* it gets a bit more complex than this, as often in CST you'll switch up to a more complex movement once you get your performance to a certain level...