Yes, it is legal. In fact, Jason Garrett did this.
But what about when a coach ices his own kicker?
That’s essentially what Dallas Cowboys head coach Jason Garrett did on
Sunday during a game against the Arizona Cardinals. With the score
tied at 13, and just seven seconds left in regulation, Dallas rookie
kicker Dan Bailey lined up for a potential game-winning 49-yard field
goal. Right before the snap, Garrett called timeout. Bailey kicked it
anyway, and nailed it. His second attempt? Not so good — he shanked it
wide left. The game went into overtime, and Dallas ended up losing
Here’s how Garrett explained his decision during his post-game press
“The play clock was running down. We just wanted to make sure that he
had a real clean opportunity at it,” Dallas coach Jason Garrett
explained. “It was at about 6 (seconds) and we were still getting
settled in, so we banged a time out to give him the opportunity to get
the snap, hold and kick as clean as possible.”
In summary, Garrett "iced his own kicker" because the offense wasn't quite ready for the play, which was a "practice attempt" that backfired on the actual field goal attempt.