Bahrudin Atajic got off the mark for Celtic as Neil Lennon's side made it 12 goals in two matches since their European exit with a convincing Scottish Premiership win at Fir Park.
Celtic dominated throughout against a Motherwell side who failed to lift a sparse home support following their shock William Hill Scottish Cup defeat by Albion Rovers, as the visitors followed their 7-0 win at Hearts with a 5-0 triumph.
Kris Commons opened the scoring two minutes before half-time with a backheel and netted a rebound after Efe Ambrose had headed the second. Anthony Stokes and Atajic finished the rout to send Celtic into their final Champions League game of the season in Barcelona on Tuesday on a high.
Celtic took the lead after smart play from Izaguirre and Lustig opened up the home defence. Pukki's driven cross found Stokes at the far post and he fired a wayward shot that Commons flicked home with his back to goal from four yards.
Celtic doubled their lead in simple fashion in the 54th minute when Ambrose rose at the back post to head home a floated corner from Mulgrew.
There was to be no response from Motherwell as Celtic created a stream of chances. Lustig played in the overlapping Brown but Nielsen blocked before Stokes was foiled by the Faroes goalkeeper. Nielsen saved from Ledley and then parried Izaguirre's curler in the 75th minute, only to see Commons bundle home the rebound.
Celtic broke a minute later with Pukki having yards of space on the right to send a low cross to Stokes to sweep home the fourth and Atajic calmly lobbed Nielsen in the final minute after being played through with no Motherwell player near him.