He opened the scoring after seven minutes when he followed up a Jonty Roubos shot that was parried by United ‘keeper Scott Morris, tapping it into the net from an angle.
Ben Mata doubled Olympic’s lead in the 16th minute, scoring from the penalty spot.
Dan MacLennan pulled back a goal for United in the 18th minute.
Gianni Bouzoukis scored Olympic’s third goal when he got on the end of a cross and volleyed it home in the 22nd minute.
Five minutes before the break, Olympic stretched their lead to 4-1. It started with goalkeeper Scott Basalaj whose quick throw started a counter attack. Roubos fed Randall who then threaded a ball for Bouzoukis to clinically finish from 10 metres.
Ten minutes into the second spell, Jack-Henry Sinclair was the provider and Randall the finisher when Olympic scored their fifth goal.
A few minutes later, Randall completed his hat-trick with a strike from the edge of the area.
Randall’s fourth goal came courtesy of a pass from Kailan Gould.
The team have one last game left in the National League at the United Sports Centre against Cashmere Technical next Friday 25th November 7pm kick off.