cold epoxy is tough to work with...it's best to use large containers when mixing - using a small cup,it confines the mix-heats up quicker...2 part epoxy, when mixed together, produces an exothermic reaction,
that is, it produces heat as a byproduct of the chemical process taking place.
The higher the temperature of the mix, the faster the reaction takes place.
In small amounts, or thin layers, the heat is radiated away or transferred
to the surrounding air or nearby surfaces. But in quantities of sufficient thickness or volume,
the surface area of the mix, isn't great enough to allow the heat to transfer out.
As a result the heat stays in the mix, increasing the rate of reaction,
which increases the temperature of the mix. It can actually become a fire hazard.
To make epoxy cure slower, cool the components before mixing
or apply the mixed epoxy to cool surfaces, or under low temperature conditions.
Like early morning before the sun warms things up, and work in the shade.