Wikipedia gives that ,the density of a uniform continuous distribution on a set $A$ is given by $$\frac{1}{\lambda(A)}\mathbb{1}_A$$ Where $\mathbb{1}_A$ is the indicator function of $A$, ands $\lambda(A)$ a lebesgue measure of $A$ (depending of the dimension of the object we measure)
For example , if we consider the uniform continuous distribution on the unitary disk , we have : $$f_{(X,Y)}(x,y)=\frac{1}{\pi}\mathbb{1}_D(x,y) $$ If X,Y relates to the cartesian coordinates.
More precisely the question is , if being asked to give the density of the uniform law over the unitary disk for example , does the result comes from the definition we given in a first place , or would we be supposed to do a calculus using only the very known density of an uniform density on an interval $\left[a,b\right]$ ?