The two nations meet in a long-anticipated clash in Lens on Thursday, with Wales two points better off in Group B following their 2-1 win over Slovakia and England's 1-1 draw with Russia.
Bale was on target in that success against Slovakia, and will line up against England as arguably the only world-class talent on the field.
There has been speculation that England could elect to man-mark Bale but Ancelotti, who signed the attacker for Real Madrid in 2013, does not believe such a tactic will prove fruitful.
"How do England stop him?" the Italian wrote in a column for The Telegraph. "It's a difficult one. Players like Bale are very hard to control with just one player of your own. You have to shape your team to dominate the space that they use.
"That means that there cannot be large gaps between the lines of defence and midfield and a lot will depend on how the three in the heart of England's defence, Chris Smalling, Gary Cahill and Eric Dier work together.
"I can see Wales using Gareth's pace on the counter-attack and while I expect England to have the control of the game that will always be a problem for them. Gareth's speed and power is very difficult to play against and a lot of the time he draws fouls very easily. Most of the time it will be Dier's responsibility to deal with Gareth.
"There will be a lot of expectation on Gareth to give Wales that match-winning edge. He is the kind of footballer who can rise to the occasion in big games and that is what England will be worried about.
"They have the better team, but the best player on the pitch will be the Wales number 11, and sometimes that is enough."