Staged crushing combined with water addition and mixing is practiced at the mine site to prepare an oil sand slurry ready for hydrotransport. More particularly, as-mined oil sand is crushed to conveyable size (e.g. −24″) using a mobile crusher. The pre-crushed ore product is conveyed to a dry ore surge bin. Ore is withdrawn from the bin and elevated to the upper end of a slurry preparation tower having downwardly aligned process components to enable gravity feed. The ore is further crushed in stages to pumpable size (e.g. −4″) by a stack of crushers and water is added during comminution. The ore and water are mixed in a mixing box and delivered to a pump box. The surge bin and tower are relocatable. Screening and oversize reject treatment have been eliminated to achieve compactness and enable relocatability.