It's modelled in part on the Alex McLellan field from August 2010 and my last game with Grays and Chadwell now (Thurrock CC). The fielders on the On-Side in positions 3,4,5 and 6 would be your most atheletic and best catchers, these would stay on the boundary looking to thwart any attempts at putting the ball over the boundary while you settle. The gap between deep long off (4) and silly point (8) is trying to entice the batsman to try and drive the ball, which as an exponent of targeting the off-stump (When it's going right) falls straight into the trap. Hitting the ball through the off-side to score fours off of slow bowling requires a level of skill I reckon isn't that common and should be my reckoning call for a straight drive which would then bring in the potential for the edge to be found and fielders at backward point, slips and perhaps even silly point to come into play.
Again this is all theory, but I'm going to put it out there and see what people reckon.
