Spaniard Cabrera-Bello hit an extraordinary six birdies and one eagle on the front nine, before parring the final nine holes to add a third-round 63 to the rounds of 65 and 66 he posted earlier in the week.
Slattery hit an eagle and two birdies on the back nine to share the overnight lead.
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"I sunk a very long putt on the first hole and after that all the other birdies were pretty much tap-ins," Cabrera-Bello told reporters.
"Even the bogey I had was a three-putt from five feet, so it could have been better, but I'm really pleased that everything went my way.
"It was a bonus to hole my third shot for eagle on the seventh. I just threw my club up in the air because I didn't know how to celebrate! I wasn't expecting that."
Denmark's Kjeldsen hit three bogeys and two birdies to finish the day one-over-par and five shots behind the leaders, while Paul Lawrie remained in contention after carding a 63 to add to his previous 61 and 71.