Hi!
Just use the hot-plate in the kitchen! I have solder 2 waterblocks with this metod. It's perfect! On 1500-2000 watt, it takes about 2-3 minutes to heat up a big copperblock
Clean/lap both parts, and use flux. Then heat up the block, and put solder on it. Immediately when it melt, you remove it from the hot-plate with a steel ruler or someting thin. When it's cold, you lap(!) the solder-surface until it's flat and smoothly. (don't remove all the solder..

) Now you put the clean and fluxed top on the block, and place it on the hot-plate. Turn the heat on, and the solder, heat and gravity does it all! (Clamps is _NOT_ necessary!) remove the block wery careful away fom the hot-plate, when the solder is melted. Voila!