Teach to learn the triangle. Reaching out with the glove palm up and learning to field the baseball out in front. Work from the ground up. Flipping is a term used to describle playes who bring the glove up after the prestance and approach to the baseball and then attempt to get it back down to field the baseball. The baseball should be fielded out in front. Anticipating a bad hop will create poor fielding habits. Get the glove out in front and field the baseball out in front.
Proper fielding mechanics give you the best opportunity to make plays on a routine basis. Bad hops are part of the game. A ball that hops up and hits you in the chest is going to hit you in the body regardless of wether the player stays down on it or not. The problem is when players flip the glove up , anticipate a bad hop , dont reach out and let it get too deep on them. Basically the back of the fingers on the glove should be in the dirt at a slight angle. Having the fingers of the glove straight down is impossible to do and still reach out. So if your fingers are straight down the ball will get deep on you and put you in a very poor fielding posistion.
Proper Pre Stance , Proper Approach , Proper fielding mechanics depending on how the ball is hit , will go a long way to fixing these issues your talking about. Staying down on the baseball should be replaced by - Reach out.