They actually have an example in the repo already, it's for d3d10 but is easily adapted to d3d11.
If I remember rightly the crux to magic is that there exists a WPF control called D3DImage but it only works with d3d9 surfaces; you therefore need to setup both d3d11 and d3d9 contexts along with a shared texture between the two. Then d3d11 can just render the scene to that texture which is subsequently used to draw the control.
that d3d10 example produces nothing for me but empty window, same with directx9 sample. many post of "magic" solutions on the net yet not a single working sample
works on any of five different directx 11 hardware. i dont have old hardware to test with so i cant tell if any slimdx wpf anything works at all.
can anyone confirm any actually working slimdx/wpf .net 4 anyhting on dx11 card ?