"It was a putt I felt comfortable over straight away and it was an easy putt by my mind," said the Royal Auckland member.
"I am really happy with the way our boys have fought back the past couple of days."
New Zealand rep Sam An was another of Auckland's heroes on the final day of pool play as he made nine birdies in 13 holes to win 6 and 4 against Adam Church.
Auckland, who have not won the title since 1995, have made a remarkable comeback to reach the semifinals after they suffered a shock defeat against Northland and then lost a close battle with Canterbury.
"We didn't expect to be in this position after the first two rounds so it has been a good couple of days," said Fox.
In the other decisive match in division one, Canterbury confirmed their place in the final four with a comfortable 5-0 win over Hawkes Bay.
"We stepped up today and played really well," said manager Rod Hayes.
On the other side of the draw, Bay of Plenty progressed as the only undefeated team with six wins from six matches in division two.
The Bay booked their place in the semifinals tomorrow with an emphatic 4 to win over Aorangi South Canterbury.
Southland play Auckland today and Bay of Plenty are up against Canterbury with both semifinals teeing off at 7.30am. The final tees off at 12.30pm.