30+ years ago, I started casting with a 10lb Lee bottom pour. The lead I was getting at the time was from the range at work which was swaged hollow-base wad cutters. To help heat up the melt I cut a tin can lid and placed it over the lead pot. The molds could then be placed on the lid so my the time the melt was up to temp so were the molds. I never saw the need for a hot plate.
I generally smelt into ingots using a SAECO cast ingot mold. When I start casting I place an ingot on the edge of the pot so that it is pre-heated before it could be placed into the pot without affecting the melt temp too much. Having cast for many years before I ever got a thermometer I learned from Dad and other casters to judge temp by watching the sprue cool. If it took to long - it's too hot. I also learned that pouring onto the sprueplate to the left side of the holes the melt would swirl into both and gave good fill. I also learned that if I watch the sprue frost over the mold was good to open. If doing 200 grain or larger boolits use two molds and rotate. Little tiny NOE 225-62 RN I could just fill the mold, blow on the sprue and open when solid.
I finally did get a thermometer and who knew, my pot was at a good range. I learned from others here about speed casting which worked well for me using two molds. BTW, most of my molds are Lee aluminum with a couple SAECO steel molds. I get a good rhythm and I can make a lot of pretty boolits.