Okay, my opinion, here goes...
First of all, be clear with yourself what you're hoping to get from this. What would his ideal reaction be from your POV? What are you looking for? You talk about not knowing "if he likes you like that" - does he have to
like you like that for this to be good, beause if it does, he probably needs to be agreeable to more than just being tied up by you.
Second, know yourself. Know your own experiences, what you like and dislike, what you still need to find out because I guarantee if you haven't prepared in terms of knowing that, that will cause problems later when trying to introduce it.
Ok, so now for breaking it to him. Like basically everyone else on here I say do NOT try to trick him. That would only come out well for you if he likes you in a certain way AND likes being tied up in the way you want to tie him up - the odds are against this. Maybe tell a funny story (can either be true or made up) that involves you tying someone up. At that point you could say something like: "So she struggled but she couldn't get out because I'm too good at tying" and add as a side-note "For example, if I tied you up, you would not be able to get out" - say it with a genuine friendly smile and see how he reacts. Slightly pause in your story and see if he decides to say anything. He MAY suggest you tie him up and you might really get lucky by getting into a situation where it becomes a sort of bet, where the stakes are what you're allowed to do if he can't escape. That's just one idea and this is where Point 2 comes in - it does rely on you being good at tying someone up so they can't escape.
If you come up with a situation like that, it gives HIM a chance to go for it. What you're going for is a no-risk way of introducing the idea - you bring up the topic, but the actual doing of it is suggested (or at least consented) by him. If you don't get an encouraging reaction, you can just move on (in the idea above, you'd finish the story), and he'll never know you were trying to work towards something.
Last point: I do not pretend to be an expert on this subject; just writing some advice which I hope you find helpful
