Graham Henry's side were 32-0 to the good at the break as Sitiveni Sivivatu, Slade, Andrew Hore and Adam Thomson all crossed, with Slade also adding two penalties and three conversions in a composed first-half display.
The All Blacks failed to add to their tally during a poor third quarter but scores from Conrad Smith, Piri Weepu and Mils Muliaina, plus a penalty try, rounded off the win.
But Henry will know his side have plenty to work to do, particularly at the line-out, ahead of next weekend's Tri Nations meeting against South Africa.
Fiji battled gamely throughout and got deserved reward through two excellent tries from Nemia Serelevu and replacement Vereniki Goneva.
Slade had booted the hosts into an early lead after Sivivatu forced Timoci Nagusa to hold on under pressure.
And the first try rapidly followed as a series of strong scrums secured possession for the hosts.
The ball was worked through the phases and Slade and Muliaina combined to send Sivivatu in for his 28th Test try.
Fiji were typically committed in defence with several crunching hits going in, and it appeared to unsettle New Zealand as several passes went to ground.
But the visitors' scrummaging travails continued as another collapse allowed Slade to slot his second penalty for an 11-0 lead after 21 minutes.
It was soon 18-0 as Slade picked up his first Test try, chipping over the front line of defence and gathering the ball after it came back off a post to slide over - the fly-half also added the conversion.
Seremaia Bai was off target with Fiji's first genuine scoring chance in the 32nd minute and they fell further behind when hooker Hore finished off a sweeping All Blacks attack.
Sivivatu and centre Ma'a Nonu were heavily involved with debutant lock Jarrad Hoeata giving the scoring pass out wide and Slade expertly knocked over the testing conversion.
Flanker Thomson then burrowed over for New Zealand's fourth try as half-time closed in, Slade again adding the extras for a 32-0 interval lead.
There was a moment of worry for the hosts early in the second stanza as Jimmy Cowan saw his clearance charged down, but Slade was on hand to rescue the situation.
The South Sea Islanders dominated the third quarter and got their reward as flanker Dominiko Waqaniburotu capitalised on a turnover to streak away, his inside pass found Serelevu to allow the scrum-half to stroll over. Bai added the extras.
The All Blacks eventually snapped out of their daze as centre Smith finished off a clever set move.
Replacement scrum-half Weepu's perfect grubber ahead from a scrum gave Smith the task of dotting down without a defender near him, Slade was again on target with the conversion.
Weepu himself then went over as another chip cut Fiji apart, with fellow substitute Ben Smith giving him a canter to the line. Dan Carter, on for Slade, added the conversion.
But Fiji immediately hit back with arguably the try of the night from Goneva.
The winger shook off a Conrad Smith tackle before twice kicking ahead to beat the cover and dot down, with Bai kicking his second conversion.
However, the All Blacks had the last word as a series of scrum penalties close to the Fiji line resulted in referee Stuart Dickinson awarding a penalty try, before Muliaina crossed on the hooter.
Carter added both conversions to move to within two points of reclaiming top spot in the list of Test points scorers from Jonny Wilkinson.
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