George Hendy scored a hat-trick as Northampton made it maximum points from their first two European games with an eight-try thrashing of the Bulls.
Sleightholme scored two tries and Henry Pollock scored the fourth try before the hour mark as a dominant Northampton side cut loose in the second half.
The visitors were still in the game with the score fourteen-five at the interval but a sin-binning to forward Alulutho Tshakweni in the 53rd minute for a unnecessary trip proved very costly and they did not score a point in the final forty minutes.
England fly-half Fin Smith contributed 10 points with the boot as Saints moved to the summit of their pool on superior points difference from defending champions Bordeaux with both sides on 10 points.
Fin Smith kicked 10 points in a man-of-the-match performance.
The nature of this victory, following a 35-27 victory on the road at Pau previously, means last season's runners-up Saints could not have hoped for a better start as they look to improve on that this season.
Bulls fly-half Kade Wolhuter missed an early penalty before the hosts opened the scoring when Henry Pollock broke before feeding Ollie Sleightholme who showed his pace to race clear to the line.
But an mistake from Sleightholme allowed the Bulls back into the game as the ball was knocked on in contact, allowing Bulls wing Stravino Jacobs to hack the ball forward and show blistering pace of his own to score after 22 minutes.
Ten minutes later, Saints had their second as quick hands from Alex Mitchell at the ruck base and then Smith sent Hendy over to make it fourteen to five at the break.
Saints were on top in both ball and field position and were being aided from Bulls fly-half Kade Wolhuter who failed to find touch with clearing penalties to reinvite pressure onto the away side.
That proved decisive after 48 minutes when Fin Smith was again the creator, darting inside to wrong-foot the advancing defence before delivering a sweet grubber kick over the line for Hendy to grab his second try and Saints' third score.
Bulls prop Tshakweni was then sin-binned for a tripping offense on Iyogun. Tshakweni was insistent he had been responding to a trip momentarily before by the Saints player but the contact from the Saints replacement prop was ruled accidental when reviewed by the match officials.
Saints seized the opportunity of having the numerical advantage to clinch the bonus point through Pollock before Alex Coles and Ollie Sleightholme scored as the hosts notched three scores in five frantic minutes.
Hendy wrapped up his hat-trick with twelve minutes left on the clock and Kemeny strolled in for the eighth and final try of an excellent afternoon for Northampton in the final minute.
Rematch of Last Year's Final Awaits Saints
The leading pair in the pool meet in a rerun of last year's final when the tournament resumes in the new year as Saints head to Bordeaux-Bègles. Northampton then conclude the pool stage with a fixture at home against Scarlets on January 18th.
The Pretoria Bulls, who have one point from their opening two games, welcome Bristol Bears next before traveling to face Pau.
Line-ups
Northampton: Furbank; Sleightholme, Hutchinson, Dingwall, Hendy; F Smith, Mitchell; Fischetti, Wright, Davison, Coles, Van der Mescht, Kemeny, Pearson, Pollock
Replacements: R Smith, Iyogun, Kundiona, Munga, Prowse, Graham, James, Thame
Bulls: Williams; Petersen, Gans, Vorster, Jacobs; Wolhuter, Burger; Tshakweni, Van der Merwe, Smith, Wiese, Van Heerden, Coetzee, Ludwig, Louw
Replacements: Else, Sithole, Mchunu, Gumede, Carr, Papier, Johannes, Van Niekerk
Yellow card: Tshakweni (53)
Match Officials
Referee: Hollie Davidson (Sco)
Assistant referees: Rob McDowell (Sco) and Dave Sutherland (Sco)