1. Mount a tube two sizes too small (ie: 20-inch tube for a 26-inch wheel) to a non-tubeless rim and tighten the valve stem nut, then fillet the tube down the center to create a big, flappy rim strip.
2. Install one side of the tire so that the tube sticks out between the rim and tire, then pour in 60-100 milliliters of latex-based tire sealant.
3. Seat second bead. Coat the rim/tube/tire interface with a mix of soap and water, heavy on the soap. Use a large CO2 or air compressor to mount the tire (don’t even think about trying this with a floor pump). Watch for air bubbles coming through at the bead and try to get the sealant to coat any areas leaking air. Trim off the excess rim strip, leaving a slight overhang.
WARNING: Non-tubeless tires are okay, but make sure the tire fits tightly on the rim. Loose fits lead to air burps or bead failures, which can lead to lost teeth. Even if done right, this setup can still lead to lost teeth, which can make it difficult to eat your corn on the cob. As always, DIY at your own risk.