Just use an empty super or just knock a simple eke up 4 pieces of 2x1 batten with a nail in each corner or even gaffer taped up, I think spreading out the paste might increase the amount of fumes for a shorter time, not good.
Yes - you can do whatever you fancy but it is defitely not to be recommended. In short just do as it says on the tin!!! A shallow eke is as simple as it gets.
dont like doing it, but when no eke available I have just put the roof on the top of the brood and apiguard tub without a crown board...the stops in the roof act as an eke
If you buy Apiguard in the bulk tubs you get waxed card squares to put your 50g on. I have a couple of hives without ekes on and simply scraped the contents of the foil tray onto the foil lid and laid that flat on the top bars; the bees have cleared most of the Apiguard so it has certainly worked.