Go to the other side of the bed and run your fingers slowly from his left thigh down to his foot. Then fasten a loop around his left ankle and tie it to the corner of the bed frame. Again, make sure that he is fully extended, but not stretched too far to remain in that position for a while.
Ask him, “Are you sure you’re ready for this? You know what they say, ‘Be careful what you wish for.’ Once I have your other arm secured, you won’t be able to get away. I’ll be able to stroke your cock for as long as I want, and I may not even decide to let you cum. Should I finish tying you up?”
Don’t move on until he says yes. If you need to give him some encouragement, run your hand up his left leg towards his cock, but don’t touch it yet. He’ll eventually cave in and agree to let you finish securing him to the bed.