Saints opened their East of Scotland Football League campaign in the sweltering heat with a 2-0 win away from home to Ormiston.
The three points, two goals and clean sheet delighted to United gaffer.
“We did a very professional job, which is what I’d asked of them before the game,” said King.
"It’s not often we get clean sheets either so I’m absolutely delighted with that.
"We had a few trialists and changed our shape a bit so it was a bit of a shock to the system for the players, but sometimes you find that can work in your favour.
"We didn’t drum it into them all week so they didn’t have that pressure, and then it works.
"I can’t complain, it was the perfect day.”
King remains on the lookout for some permanent signings, but believes he got his team selection, which saw the manager himself take to the field in midfield, bang on.
"Having to play myself with Paul Quinn, who has been around the game for a long time, in the middle of the park with Jason Penman on one side and a trialist on the other gave us plenty experience in there,” he said.
"We played some really good stuff at times on what was a horrible park and not the best of days for it.
"We had an idea what we’d be up against with Ormiston, we knew they’re a decent team with young players.”
United are now aiming to build on Saturday’s win when they host Craigroyston this Saturday.
The weekend’s visitors played their first game of the campaign in midweek, going down 2-1 at Kennoway.
King took in that game, and believes his side will have to be on their guard against a team which impressed him.
"We need to manage it on Saturday against what was quite an exciting team at times when they got the ball down,” said the manager.
"They put in a lot of work on what was a hot night so we can only hope that them having to travel again up to St Andrews on Saturday can be a bonus for us.
"There were a few of them dead on their feet so we need to try and capitalise on that.
"They will start frantic and we have to manage that properly and be patient throughout the game.”