The White Wolves, smarting from being held 3-3 at title rivals Wyberton on Wednesday, showed no mercy to Saturday's opponents, chalking up an unassailable 14-0 half-time lead to roar into the competition's last 16 as they aim to beat their previous best of being semi-finalists.
Jordan Smith led the way with four goals with a hat-trick for Bailey Wright, two each for Bradley Coulam and Ollie Webber and one apiece for Paul Coulam, Mitch Taylor, Alex Aldrich and Frazer Chapman.
“They play two or three levels below us but, fair play to them, they kept going,” said boss Carl Martin.
“We made four changes at half-time which probably interrupted our flow and the tempo wasn't there, but it is hard to motivate yourself when the job is finished at half-time.
“They didn't give up which was testament to their manager really.
“We had already made four changes from Wednesday to try to get everybody a run who haven't featured much so all in all we are really pleased.”
Louth were 4-0 up inside 10 blistering minutes and had hit double figures by the 27th minute.
But Sleaford pulled one back on 56 minutes before Louth added their last goal 10 minutes from time.
In midweek Louth had led 2-0 at Wyberton before trailing 3-2 after a floodlight failure interruption only for Smith to bag his second from the spot in the ninth added minute.
“We were 2-0 up and cruising before they scored a speculative shot from about 35 yards,” said Martin.
“We had enough chances to win two or three games to finish them off second half. But they are league champions and county cup winners and they kept going and peppered us.
“We defended really well until their keeper scored straight out of his hands, on the wind, and over our keeper's head. As soon as it bounced you could see our keeper was struggling. You can't legislate for goals like that – it was a freak of nature.
“Their third was a 25 yard 'worldie', so all their three came from outside our box.
“So to get a last minute penalty and a point was a good result, but it does feel like two points dropped and we are really disappointed.”
On Saturday Louth head for Sleaford Town Rangers, who sit third from bottom. But Martin warned: “We lost 1-0 there last year or the year before so we know our mindset has to be right and we can't take anything for granted or they will take full advantage.
“But we go there really confident and looking to come away with the three points.”