An apparatus for preparation of an electrophoresis slab gel may include a base having an opening configured to receive a cassette configured to contain an electrophoresis slab gel, a clamping mechanism configured to move relative to the base between an open position in which the clamping mechanism permits insertion of a cassette into the base, and a closed position in which the clamping mechanism is configured to clamp a cassette received in the base, a compressible pad operatively coupled to the clamping mechanism in a position to compress against a cassette received in the base in the closed position of the clamping mechanism. The cassette may include a first plate and a second plate, and a spacer mechanism separate from each of the first and second plates, the spacer mechanism configured to be positioned between the inner faces of the first plate and the second plate. When subjected to a clamping force exerted on the outer faces of the first and second plates, the spacer mechanism is configured to maintain a separation distance between the inner faces of the first and second plates, and provide a seal to prevent leakage of an electrophoresis gel solution introduced between the plates.