Clean the concrete floor on which you intend to install the cork underlayment. Unless the floor is greasy, running a wet mop over the floor removes most of the dust and debris. If the floor does have greasy-spots, add a little grease-fighting dish soap to the water and rinse the floor with a clean mop once you get the greasy spots up.
Measure the length of the concrete floor with a tape measure once it dries. Roll the cork underlayment out across the floor and measure the same distance down one side of the cork, marking the edge of the underlayment with a marker, and then measure down the other side of the cork underlayment and mark the distance again with a marker. Lay a straightedge across the cork underlayment between the two side marks, draw a line and cut the underlayment across this line with a utility knife.
Cut additional pieces of cork underlayment using the same method until you have enough underlayment to cover the entire floor. Put each piece down in its place on the floor to make sure the floor is completely covered once you lay the underlayment out. If you must cut pieces shorter than the full length of the room and place pieces end-to-end, arrange the pieces so that no seams in the underlayment are directly next to each other.
Lift one row of cork underlayment from the center of the floor, leaving the rest of the underlayment in place, and snap a chalk line down the side of the adjacent row of underlayment. Once you make the chalk line, lift the row of underlayment directly next to the line.
Spread a 1/8-inch layer of latex thin-set mortar on the center of the floor where the two removed rows of cork underlayment were laying. When you get to the outside edges of the area by the cork underlayment still on the floor, slide the next rows of underlayment out of the way to prevent getting mortar on them.
Press the rows of cork underlayment that you removed from the floor back down into their places in the mortar. Slide the edges of the underlayment together until they sit tightly against each other.
Continue out from the center rows of the cork underlayment. Lift the next rows out from the center, spread adhesive and then press the cork underlayment back down into place.
Push a floor roller over the cork underlayment to press it firmly down into the adhesive and remove any air pockets underneath. Cork underlayment manufacturer Manton recommends a 50- to 100-lb. floor roller.