The seat tube clamp is not attached in any way to the tubing. I did cut 4 slots in the tubing so it could be clamped down tight on the stem that you see below. You have to tighten the bolt really tight to keep the tube from wiggling back-and-forth on the stem.
Once upon a time ... there was an angled section attached to the side of the stem ... which went forth and clamped to the handlebar. I cut that off with a hacksaw and ground it smooth. I inserted this like normal into the headset, tightened it really tight (doesn't matter which direction this faces ... only you will know what's under the tubing), then slide the tubing down over the stem top to the headset nuts, and clamp it (making sure the handlebar is perpendicular to the wheel).