Williamson ether synthesis involves nucleophilic substitution (S$N_2$) where an alkoxide ion attacks an alkyl halide. To form the desired unsymmetrical ether, the alkoxide should be derived from the less sterically hindered primary alcohol, and the halide should be a primary or methyl halide to avoid competing elimination. The target ether has a phenyl group attached to oxygen and a primary alkyl chain. The phenyl group is stable and won't undergo elimination, so the alkoxide should be phenoxide. The halide must be primary to ensure good S$N_2$ reactivity.

Final Answer: Sodium phenoxide and 1-Bromopropane