I apply eis to fondant all the time. Here is how I do it. Take a brush, I usually use about a half inch one. Brush a small
amount of water onto your fondant, which is already applied to the cookie. Spread it out just a bit smaller than the the size of the ei you are applying. Brush it a bit until the fondant is sticky, again, staying within the space a little smaller than your ei
Lay your ei on the fondant, you will have a second or two to manipulate the ei, so that damp fondant will come to the edges of your ei. If I am doing squares, I dip each corner of the ei into the sticky fondant before applying. That makes sure the corners stay down. Very seldom do the edges come up and I never outline my eis with anything.