"It's a huge achievement," said Slew, "massive.
"You look at the teams around us, the money they've pumped into their clubs, we don't have the budgets they have, so to do what we've done and finish where we've finished, I think it's a great achievement.
"We've got quality players, right from when I came in in July, I knew we were always going to end up in the top four or five, I knew we were going to end up in the play-offs, minimum.
"We've just got great players and I think it's shown throughout the season how good we actually are."
On The Shaymen's chances, Slew said: "We're very confident. Obviously it's going to be a tough test but we've had a good week's training and we're ready to go.
"We've just got to focus on what we've been doing all season and hopefully get the win."
Slew says the winner will all depend on who handles the occasion better.
"It's different, obviously you're playing league games all year and then the play-offs, all the form goes out the window, it's just a one-off game, the best team wins and hopefully that's us," he said.
"Emotions will be running high, and I think it's down to who controls the emotions.
"We're at home as well so we've got that advantage, we've been awesome at home this year, and hopefully we take that form into this game."
Town won more home games and conceded fewer home goals than any other team in the National League this campaign, and feels the Halifax fans will be crucial during the tie.
"They've backed us all season, even when we've not done so well in certain games, they've always been behind us," he said.
"I think we're going to need them tomorrow more than we've ever needed them."
Slew accepts winning their next three matches in a row, if they reach the final, would be difficult, but feels Town are capable of going all the way.
"All three of the games are going to be tough if we get to the final, but I don't think one team will be so much harder than the other," he said.
"It's just up to us really, I think we'll win it or we'll lose it.
"Hopefully we're mentally prepped and physically prepped and we can get the job done.
"With the clubs we're going up against with these big budgets, I think its a huge achievement to finish where we've finished and hopefully we go all the way.
Slew is Town's third top-scorer this season, and feels raring to go for the game.
"I'm at the fittest I've been all season and mentally I just feel ready to get the job done," he said.
"Obviously we wanted to win the league but we can't do that so we'll try and win the play-offs. I'm a born winner so all I want to do is get through the quarters, get through the semis and then win that final.
"It would be nice to get a couple of goals in the play-offs, but the main thing is we win. I wouldn't care if I didn't score for the next three games if we win."