No-one bid the Slam here but it is certain to make. I'm showing three auctions that might have got you there.

If you play a 2♥ Opening as weak then it is a good idea to play a 2NT Response as OGUST, showing 15+HCP and asking about the strength of opener's hand and their trump suit.

After an OGUST 2NT then 3♣ shows weak hand/weak suit; 3♦ a weak hand/strong suit; 3♥ (as here) a strong hand/weak suit; and 3♠ a strong hand/strong suit.

After 3♥  then 3♠ , 4♣ and 4♦ are Cue-Bids showing 1st round control (Ace or Void) in the suit bid. 5♣ shows 2nd Round Control (King or Singleton) since 1st Round Control has already been shown.

Once North knows there are no Club Losers they should confidently bid 6♥ 

If South Passes and N-S are playing 4-card Majors North will open 1♥ 

3♠ is a Splinter showing Game Values with a singleton Spade. Although short on points South's shape is so perfect that it justifies this bid (for those playing Losing Trick Count then South's LTC=7).

4♦ is a Cue-Bid and 4NT is Roman Key-Card Blackwood asking how many of Five Key Cards does North have. The Five Key Cards being the four Aces and the King of Trumps.

North's 5♦ shows zero or four of these Five Key Cards. Since North just might have Zero South bids 5♥ which North converts to 6♥ because they have Four Key Cards.

If N-S are playing 5-card Majors and South decides not to open then North will open 1♣ and South should jump to 2♥ showing a 6-card suit and near-opening values.

Since 2♠ by North would be forcing 3♠ is a Cue-Bid agreeing Hearts and showing first round control in Spades

Now the Auction can continue via Cue-bidding to 6♥ as in the first example where South opens a weak 2♥