Assuming force, length, and time to be the fundamental quantities,...

Energy is defined as the capacity to do work, and work is the product of force and displacement.

Therefore, the dimensional formula for energy can be written as:

$[\text{Energy}] = [\text{Force}] \times [\text{Displacement}]$

Substituting the fundamental quantities given in the problem, where force is $F$ and length (displacement) is $L$:

$[\text{Energy}] = F \times L = FL$