LED lights and heatsink
Typically, high wattage LEDs can use passive cooling, if calculated correctly. The higher the wattage, the more crucial it is. Math aside (because I don't have it), it's essentially some square inches/cm of copper or similar per watt of heat. Finned heatsinks provide a high area in a small package. Alternatively, you can use fans or pelters or other active cooling methods.

But Even 1W led stars can use a simple metal plate to provide that passive cooling. As long as you have good thermal conduction (i.e. metal on metal or through thermal conductive material), a large metal plate works great. Metal U or N channel as well. Steel, Aluminum, Copper (if you have the money), not really crucial which.

Screw or glue a metal plate to the cupboard underside then affix the led module to it. You can use special thermal epoxy, or even something like JB Metal Weld. I am not sure how well standard thermal paste for cpus (Artic Silver) will work. When old and dried, thermal paste can hold it in place, but when fresh, it might not hold a module upside down. Some led modules can just be screwed onto the plate (Pre-drill a smaller hole, and use self tapping screws, or nuts and bolts (if you have access to the other side), or use a tapping set).

Then again, looking at the picture again, those are standard 5050 leds. Heating won't really be a concern, and the pictures of the back, they arn't designed for mounting like 1W or higher led stars would be. These are basically like the simple led strips are. Don't worry about heatsinking. These can be superglued or even hotglued.