Isak and Van de Ven have sorted it out between themselves after the Sweden forward was forced off during Saturday's Premier League clash, Frank added.
Slot said that Van de Ven's challenge on Isak, made as the Sweden forward scored the first goal in Liverpool's 2-1 win, would have caused serious injury 10 out of 10 times.
"Obviously, I'm disagreeing... we're talking about a defender that will do everything to avoid (conceding) the goal. It’s a transition so he is sprinting back in. There’s a ball slid down in the side and he does everything he can to block that," Frank told reporters on Tuesday.
"Unfortunately, Isak has planted his foot straight there which makes it look worse than it is... put it this way, if my defender doesn’t do that, I don’t think they are true defenders. I don’t see that at all. I think reckless challenges, normally, you haven’t seen any from Micky.
"I also know the two players have sorted it out, so that’s a good sign."
Saturday's loss left Spurs 14th in the table, with one win in their last eight league matches ahead of Sunday's visit to eighth-placed Crystal Palace, who are four points above Frank's team.
Frank credited manager Oliver Glasner, who led Palace to their first FA Cup triumph this year, for the strong start to their league campaign after a 12th-place finish last season.
"I think Oliver's done a top job at Palace. Very impressive. Clear identity of the team. Defend low, very compact and difficult to break down and very good on the counters," Frank said. "They're one of the best on corners and have added long throws."