Clothes designer Frances beat former model Ruby Tandoh, 21, and psychologist Kimberley Wilson, 30, in the final.
Frances impressed judges Paul Hollywood and Mary Berry with a rainbow-style savoury picnic pie and showstopper three-tier wedding cake, inspired by William Shakespeare's A Midsummer Night's Dream.
She had to keep the news under wraps for a few months.
"I've been back at work and trying to keep a poker face," she said.
"I remember watching the Wimbledon final the following week and getting so emotional... and thinking at least Andy Murray doesn't have to hide his trophy under his bed for the next three months.
"I'm looking forward to being able to celebrate."
She dismissed reports about chemistry between Paul and Ruby, who was crowned star baker three times during the series. "We were not thinking about any of that in there," she said. "There was no flirtation."
She admitted that there was some flirtation elsewhere in the Bake Off tent, though.
"We (the contestants) were each flirting with each other if we needed to, for more parchment paper or another spoon if they were still being washed up out the back," she quipped.
Frances took a break from baking after winning the show. "I thought my blood sugar levels would go through the roof," she said. "I had a bit of a sabbatical."
She is considering producing a book. "The baking market is completely saturated so I don't want to do a book that's anything like one that's already out there. I'd like to create a book that's got all my rough sketches and ideas."
Judge Paul Hollywood called Frances "a deserving winner".
"When it came to the showstopper she just beat the other two guys hands down," he said.
"She not only gave us the style, she gave us the substance too and that cake actually, each layer, superb."
Mary Berry said, "Frances has many qualities, she has attention to detail, she's got excellent flavours, her baking improved as each week went by, we're very proud of her."