Kelsea Ballerini recently got to spend some time as a coach on The Voice, filling in for Kelly Clarkson as she recovered from a sinus infection. Now, as her episodes on the show have aired, Ballerini appeared on Clarkson's The Kelly Clarkson Show to recap some behind-the-scenes moments and share how closely Clarkson kept in touch with her during her time on set.

"We were in constant contact all week," Clarkson points out. "I think people are probably gonna see you on your phone a lot and think you're just texting your friends or something, but we were texting the entire time on the show."

"You helped me so much!" Ballerini replies, adding that she needed as much extra briefing as she could get, since she got the invitation to fill in on the show with less than 24 hours notice.

"Kelly called me at 7PM Nashville time, and they were shooting the next day at 1PM in L.A.," she says. "I fully went back to college. On the flight over, she sent me all of the blind auditions, everything about everyone on her team: What she loved, what she was looking for ... You just downloaded all of your incredible knowledge."

But when she first got on set, Ballerini says that her immediate concern wasn't the show itself, but rather how cold it was sitting in The Voice's signature coaches' thrones.

"When I got in the chair, I was like, 'First of all, where's that seat-warmer that you were telling me about, because it is cold," she jokes.

"I told you! I was like, 'Look for the seat-warmer. Your butt is gonna be so cold,'" Clarkson replies. "And I wear Spanx, girl! I'm all covered up, and I ain't as thin as you, and I'm cold! You had to be dying!"

The seat-warmers were apparently a 2018 addition to The Voice's set chairs, during the same season that the show brought Clarkson on as a full-time coach. Per Yahoo! Entertainment, the "premium adjustable seat-heaters" feature was only one of a number of upgrades unveiled that season, such as the thrones' spiffy metallic automobile-paint finishes and chrome cup-holders that coach Blake Shelton specifically requested.

Of course, the most famed feature introduced that year was the "block" button, which allowed coaches to prevent each other from recruiting contestants to their teams.

The Voice airs on Mondays and Tuesdays at 8PM ET on NBC.

WATCH: Has The Voice Changed Blake Shelton?

 The Voice Stars, Then + Now:

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