Originally Posted by
sean.hwy
I am not sure how putting the hole on top with your finger on the hole and all the sealant pooled at the bottom of the tire would do anything.
One school of thought is that if the hole is submerged in sealant then the sealant can't dry to form the plug. But I think it depends on the sealant itself. Some thicker sealants with added fibers are probably more effective at sealing with the puncture on the bottom, while less viscous sealants with better after spinning the wheel a bit to evenly coat the tire, then don't let the sealant pool on the hole, and rely on the air pressure to force smaller droplets into the hole and allow it to dry quickly for the seal to form.