I am in the minority here. I do not like the slot against two checkers on the bar. I prefer the orthodox method of waiting for my opponent to enter with one checker. Then I will try to hit loose, leaving the slot, or else to hit Black's outside blot. To this end, 11/5, 13/10(2) has an advantage over the 11/5, 24/21, 13/10 I recommened above. The checker on the 24 point can hit with sixes, while the checker on the 21 point duplicates the three Black is planning to play 6/3.

I agree that getting sent back will aid Black by delaying him. I disagree that that makes the slot acceptable. My priority is to prevent White from making the three point. The best play for that is not to slot.

This would be fine if white didn't have any points. But since he has two points, you aren't as likely to be able to keep sending him back to the bar.

For example, let's say you had the 1 and 2 points instead of white. Now it makes sense to hang back and leave the spare to attack because if he rolls 32 and only gets one checker in, you've got a shot at hitting him and he's more likely than not to stay on the bar on the next roll. But here, let's say he rolls 32. Yes, you still have your chance to hit, but if you miss he has a double-direct to cover.

You might object because if he rolls 32 after you've slotted, you're worse off. But those types of situations are not the most common. It's more common for him to get only one checker in, and for it to NOT hit on the 3 point. This will give you a double direct to cover the 3 (which you do not mind dismantling your 8 or 7 point to do) plus the indirect 7 to cover as well.

The best way to prevent white from making it is to make it yourself. Therefore, as uberkuber stated:

Thanks, Aaron, for this explanation. You make a strong argument that even I can understand.