Combination waste collection unit

A method of using a combination waste collection unit, comprising:

• placing a first tray along a floor, the tray having a unitary structure with a base and four sidewalls extending upwardly around a perimeter of the base, the tray defining a container area, wherein:
• the base includes a sloped surface sloping downwards from a first sidewall of the sidewalls towards a second sidewall of the sidewalls, the second sidewall positioned opposite the first sidewall;
• and the tray defines a trough along the second sidewall and within the base, the trough having a greater depth in the container area than the sloped surface;
• and the sloped surface includes a plurality of fasteners;
• positioning a first pad of a plurality of pads along the sloped surface of the base such that a plurality of opposing fasteners of the pad each align with a respective fastener of the base, and removably coupling the opposing fasteners to the fasteners, wherein:
• each pad is sized and shaped to cover the sloped surface;
• each pad is configured to absorb liquid;
• each pad includes a non-absorbent pull-tab along a perimeter of the pad;
• removing the first pad from the tray by pulling the pull-tab away from the tray to de-couple the fasteners and opposing fasteners;
• emptying any liquid within the trough;
• and
• positioning a second pad of the plurality pads along the sloped surface of the base such that a plurality of opposing fasteners of the second pad each align with a respective fastener of the base, and removably coupling said opposing fasteners to the fasteners.