The traditional Flex(1-4 Low set) differs from the 4 man flex in fact that the 4 man flex has 4 players running a continuity motion while the other offensive player acts as a reader of the defense and looks to exploit defensive overplays. Here some basics of the offense.
1. Starts out of a 2-3 high set. Wings can use L cuts to get to the wing position or fill out of your break package.
2. When the ball is entered to the wing (O3), the guards run a scissor cut off of the high post. Opposite guard (O2) cuts ball side off a back screen from the high post to the ball side block. The other guard (O1) rubs off of the high post to set a cross screen for the opposite wing (O4) for a reversal pass. You can run an option for an overhead lob for the guard also. The high post (O5) needs to be able to slip screens and look for dives and defensive overplays. He gets a lot of looks in this offense.
3. Once the ball is reversed from O3 to O4 (top of the key), the ball is swung to the O1 at the wing. From that point, you will use the traditional flex cuts. Opposite wing will flex cut to the ball side. Top of key player will set down screen for the flex screener. This continuity continues. As mentioned before, the high post gets a lot of good looks in this offense, especially if he has a good mid range jumper and/or is good at taking the ball to the rack. Usually it is the high post defender who sags on the flex cut, thus leaving the high post open. Ths also allows for a good high low look.
I have diagrams with other options and counters to defensive overplays if interested.
Putting a strong offensive player at that spot can be very benificial. I like a 3 man who is good at reading defensive overplays at that position. If you have a week offensive player at that position, his defender will totally take away the flex cutter. Hope that makes sense. Let me know if you have other questions.
I'd like to see what you have, too. I've run a four man flex before, like the one Dave Bliss ran at Baylor. I am just now taking over a program and would like to run flex variations throughout, so any new ideas would be helpful.