Obtain a 230C PTC Heater with at least 100W output. You can source them from Amazon or Aliexpress. I chose to use 110V mains as I did not want to bother with a high amperage DC power supply. If you are afraid of mains there are low voltage DC options available.

Find or build a suitable stand for your PTC heater; unless you have a high temperature surface it should be offset. I used an old heatsink from the Pentium II era. Be creative.

Secure the PTC heater to the heatsink. My initial test ignored this step, but I strongly recommend it for safety reasons.

Tie the PTC Heater to your power source. If using mains, please don't be stupid and observe all safety cautions.

The fun step: Populate your PCB with components and solder paste.

Place PCB directly on the PTC heater and energize the heater. For me, I saw reflow in about 90 seconds. Your time may vary depending on extensive your ground plane is on the back of your PCB, as well as other heat conduction factors (vias, etc). I found that a large ground plane did add a bit of time for those boards.

Let the reflow soak for a bit then remove from the board to cool. Don't forget to turn off your PTC Heater, or it will keep itself at its preset temperature.