Happy New Year - from all of us at Sluiceboy Prospecting!
Sluiceboxes create a straight, consistent channel, with regularly spaced slow spots created by riffles. Each riffle creates an eddy, a backflow of water that allows the gold to settle out. Material is placed at the top of the box and carried in suspension down the channel. Clean out your sluicebox with water, then pan those "concentrates" to recover the gold!