What is the best way, for a random led-light, to mount the led to the heatsink?

To understand this to some extent, and the factors involved, I've seen parts and bits of formula's, but can't find them back nor combine them to have my question answered.

When all things are clear, I can decide on the use of a star and the means of attaching. Untill then I understand little of how to calculate with this.

Led (wattage ) e.g. 35 Watt SST90, 4,5 C/W

Medium (solder / paste / glue ) e.g. solder, 0.05mm

Star (thickness, thermal conductivity, surface area) e.g. Aluminium , 1.6mm

Medium (solder / paste / glue ) e.g. paste


Note on heatsink: I think most flashlight are limited by dimensions of the heatsink and the design of the head in regards of fins to dissipate heat.

Therefore I hope to leave out discussion on heatsinks. I just want to be able to decide what the best option for mounting a Led would be, assuming the heatsink would not be the limiting factor in giving of the heat to the outside air/water.

Some reference:

Al-oxide (Cree ) 30 W/m-K

Aluminium 250 W/m-K

Copper 401 W/m-K

Silver 429 W/m-K

Arctic Alumina compund 4 W/m-K

Arctic Silver compound 9 W/m-K

Arctic Silver Epoxy 7,5 W/m-K

Air 0,026 W/m-K

Al, Si mg Alloys 200 W/m-K

Steel 45 W/m-K

Brass 85 W/m-K

Titanium 22 W/m-K

Silicum Carbide (SST) 120 W/m-K

Solder 20-30 W/m-K

High grade solder 60 W/m-K