The former Gloucester and England fly half's side were trailing 8-6 at the interval before increasing the tempo to score five unanswered tries in the second half.
"In the second half I was very pleased and to score five tries against a very good Wales side made me delighted for our guys," said Mapletoft.
"We had a similar experience in the Junior World Championship semi final against South Africa in Tokyo last summer.
"In the first half we just didn't play and then it was a case of déjà vu here with an almost identical second half when the guys came out and played.
"It's about self-belief and to be able to say 'we are better than you and we're going to show it'. I hope we can take that through the Six Nations and beyond.
"To score five tries is a testament to the ambition we have. These guys can play and they've just got to have that self-belief."
"I thought the front row were all outstanding. While I don't like singling out individual players I thought Joe Marler had an exceptional 80 minutes and just continued the way he's been playing this season for Esher."
Gloucester Rugby's Freddie Burns on the challenge ahead:
"Italy, Scotland, Ireland and France are all tough games and they'll be hard. Wales pressed us and they made life hard for us but we have to take some confidence out of it."
"We don't want to look too far ahead at titles or the game against France. Now it's all about Italy."
Gloucester Rugby centre Jonny May, on his first appearance for any England side after missing out at Under 16 and Under 18 level:
"It's my first England cap and it was brilliant running out at Kingsholm. I couldn't have had a better start. No-one was going to stop me when I got the ball...I knew I had to get there because Jackson (Wray) was outside me in loads of space."
"I had loads of friends and family from Gloucester and Swindon here, so to get on for England in front of them was a great thing."
"Every position in the squad is competitive and we've got so much strength in depth so you've got to keep putting your hand up to play."
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Content courtesy of RFU