It doesn't need to 'sit' for any amount of time (you're not making a cake
) I have steel plates which sit on a rail under the OMF, slide pan in, load the Varrox with about 2.5g OA, slide in over the pan a wedge a piece of foam in the gap, all my hives are in pairs so:
once two Varox are in place, connect both to your car battery for two minute 30 seconds
then disconnect the varrox and leave for a further 2 minutes -
the OA will start to sublimate at about 1min15 sec and will continue to sublimate after you turn off the power, the pan will be clear of OA 2 minutes after turning off the power.
You can then immediately remove the varox, dip in cold water to cool to a safe temperature,
you then only need a minute or so to switch the steel pans to the next two hives, refill the varox's (I have little plastic cosmetic pots all pre mearured ready to go) and I'm set for my next blast, so in total, two hives shouldn't take morer than six minutes which includes faffing around time/moving the battery etc.
and by the way - there is no need to fiddle around closing the entrances and shutting the bees in, the original instruction for that was when pushing the varox in from the entrance - you had to block then or risk a mad rush of bees at the entrance being cooked by the hot varrox.