Answer
Arrange in parallel two branches, in which each branch has two resistors in a series.
Work Step by Step
When we connect two resistors in a series, the equivalent resistance of that branch is:
$R_{eq}=R+R=2R.$
When we arrange two such branches (with equivalent resistances of 2R each) in parallel, the equivalent resistance is such that:
$\displaystyle \frac{1}{R_{eq}}=\frac{1}{2R}+\frac{1}{2R}=\frac{2}{2R}=\frac{1}{R}$
so, $R_{eq}=R$
