Once the butyl is in place and you have prepped the trim ring with a polyurethane or polysulfide of your comfort and choosing it's time to set the trim ring.
If you used the method I outlined it is possible to remove the clamps, for a brief period, after you've seated the butyl tape so you can install the gooped up trim ring.
Once the clamps have been removed slide the trim ring over the ports spigot/flange and re-set the clamps. Do not over tighten them and use just enough pressure to get the machine screws started from the inside.