I'm actually not interested in having evolution on Slackware, but here is what I found in the evolution 3.8.0 source package readme
. It looks like some sort of dependency hell, but it seems to be possible without a full gnome installation.
In order to build Evolution you need to have the full set of GNOME 2.6
(or greater) development libraries installed.
Please make sure you have the most recent versions of the libraries
installed, since bugs in the libraries can cause bugs in Evolution.
Additional dependencies, besides the stock GNOME libraries (the
dependencies should be compiled in the order they are listed here):
* gnome-icon-theme 1.2.0 or later
* ORBit 2.9.8 or later
* libsoup 2.2.1 or later
* evolution-data-server 1.1.1 or later
* gtkhtml 3.5.0 or later
* [Optional] Mozilla NSPR/NSS libraries
These are needed if you want to compile Evolution with SSL and S/MIME
* [Optional] gnome-spell 1.0.1 or later
This is only necessary if you want to have the spell
checking functionality in Evolution's message composer.