I've always been a fan of the idea that there's no such thing as too much rope. I'd start by crossing your wrists behind you and tying them tightly. I sit you in a chair with your hands behind the seat back and tie a rope around your wrists, through the chair back, and around your waist. Next more rope goes around your chest and waist, pinning your upper body to the chair. Of course, I'm careful and cinch all the rope. I finished your upper body by tying your thumbs together, making your hands more useless.
Moving down, I wrap rope around your upper thighs and the chair seat, making sure you're not getting up anytime soon. I move down your legs, tying and cinching rope above and below your knees, your calves, and your ankles. Just for fun, I even tie your big toes together. Now I bring out a second chair and place your bound legs on it. I thoroughly lash your legs to the seat of that chair, so that you can't bend them or pull away.
To finish you off, I use a couple of pairs of your tights to gag and blindfold you. Now you can plead to be untied or see the knots. Now, you have 30 minutes to get free, or face the consequences. What consequences? Let's just say tying your legs to the other chair put your feet out in the open for tickle torture.
Enjoy!
