Systems and methods for producing a crude product

A flexible once-through process for hydroprocessing heavy oil feedstock is disclosed. The process employs a plurality of contacting zones and at least a separation zone to convert at least a portion of the heavy oil feedstock to lower boiling hydrocarbons, forming upgraded products. The contacting zones operate under hydrocracking conditions, employing a slurry catalyst for upgrading the heavy oil feedstock. The plurality of contacting zones and separation zones are configured in a permutable fashion allowing the once-through process to be flexible operating in various modes: a sequential mode; a parallel mode; a combination of parallel and sequential mode; all online; some online and some on stand-by; some online and some off-line; a parallel mode with the effluent stream from the contacting zone being sent to at least a separation zone in series with the contacting zone; a parallel mode with the effluent stream from the contacting zone being combined with an effluent stream from at least another contacting zone and sent to the separation zone; and combinations thereof.