An electrolysis cell (10) contains a number of carbon anodes (12) having top, bottom and side surfaces, operating in molten electrolyte (17) in an aluminum electrolysis cell (10), where gas bubbles (28) are generated at the anode surfaces and where alumina particles (20) are added to the top of the molten electrolyte, where the carbon anodes (12) have one inward slot (21) passing through the carbon anode (12) along the longitudinal axis 40 of the carbon anode and also passing through only one front surface (25) of the carbon anode, where the height (32) of the slot (21) is from about 45% to 80% of the anodes thickness and the slotted front surfaces (25) are disposed toward the center of the electrolysis cell so that generated gas bubbles (28) are directed to the alumina particles.