He entered one Formula One World Championship race, the 1962 Dutch Grand Prix, with one of Carel Godin de Beaufort's Porsches, but his car was not ready in time for the event. His entry was taken by Wolfgang Seidel. Throughout the 1960s Slotemaker competed in the 24 Hours of Le Mans race, and was a driver and advisor for the "Le Mans" film in 1970.