It is critical to have proper heatsink for LEDs to maintain the temperature within the specification. Maximum operation temperature of power LED is 150 Celsius degree, however lower is always better. High operation temperature cause reduced life time, reduced brightness and higher voltage drop.
For single starboard, LGA chip heat sink or similar can be used.
For multiple starboard, bigger heatsink is required. computer CPU heatsink is readily available and good. Intel CPU heatsink without fan or Socket 478 CPU heatsink is good, since they have flat CPU-side surface
For multiple starboard, a strip of aluminum bar is popular.
To reduce the thermal resistance between LED and heatsink, it is recommend to have thermal material such as thermal adhesive tape or thermal epoxy.