The flex offense is one the oldest motion offenses there is in basketball. There are all kinds of variations of flex using different movements and different setups. One of things I like to do is run a flex screen from positions where the defense is not expecting it. One of the best places to run the flex screen is off of a baseline out of bounds play.
When running the flex on a BLOB setup, I like to start in a 1-4 low setup where all 4 players are lined up across the baseline. This flattens the defense and gives the offense a lot of space to move into.
The easiest inbounds pass to throw in this situation is over the top to the player directly in front of the inbounder. This is the forward(3) throwing the pass over the top to the big(4) in the diagram above. The forward(3) is then going to step right into the court replacing the spot the big(4) just left.
Once the big(4) catches the inbounds pass then the center(5) is going to sprint up the lane line for the pass from the big(4). This is the flex offense right from a BLOB setup in 2 passes. On the cross pass, the point(1) is going to cut across the baseline using the flex screen from the forward(3).
By having the big(4) and center(5) being the two players coming up and away from the basket, the defense will probably not have any size advantage down low so even a small point(1) should be able to shoot the ball off the flex screen without issue.
If the defense does not closeout to the big(4) or center(5), then they should have a wide open elbow jumper. If the guard(2) defender steps over into the lane to help, then a quick pass to the corner for a potential 3-point shot is open.
While this is a play with very little moving parts, it can attack the defense no matter what the defense does to stop it. I also like the fact that four of the five offensive players are doing something. Plays are harder to guard when there are more moving pieces. I also like to put my best shooter in the backside corner where the guard(2) is at because that is the most likely spot for a 3-point shot. By putting the best shooter in this spot, it can help to make sure the backside defender is away from the basket making the flex cut that much more effective.
By grouping this play with 3 or 4 other 1-4 low setup variations, this can keep the defense unsure of what the offense is doing which can lead to better shots. I always like to have 2 to 4 different plays using the same setup if the defense starts to overplay 1 play, then I can use another play to take advantage of how the defense is overplaying.
I have a series of plays using this same setup that can be used together to keep the defense off-balance and guessing what is coming from the offense.
