Attachment points for laptop cooler screw holes are generally emphatically not standard. I assume a bracket would be required. Whether doing one is even possible is another question.
laptops are rarely even taken apart, so the location and nature of the screw holes in question are unknown to me. Googling “dell e6540 motherboard” and looking at images there appear to me to be at least 3 different motherboards with that designation. The ones I do see have ZIF sockets for the CPU, but no cpu holder so the cpu is actually held down to the connector by the cooler which makes things more complicated.
It would depend on the layout of the motherboard. A mere heatspreader is very unlikely to work, and will probably be far less effective than the original stock cooler.
Adapting a full desktop cooler or keeping the cooler designed to fit is likely the only shot. As to 3d printing it may depend heavily on how strong a bracket could be produced. Many of them are soft heat set plastic and may not be strong enough to withstand the pressure needed to make a good connection. There are desktop CPU coolers that are designed to be attached with brackets and in theory one might be designed. It strikes me as difficult and perhaps not possible.