Minimal D3D11 reference implementation: An uncluttered Direct3D 11 setup & basic rendering primer / API familiarizer. Complete, runnable Windows application contained in a single function and laid out in a linear, step-by-step fashion that should be easy to follow from the code alone. ~215 LOC. No modern C++ / OOP / obscuring cruft. View on YouTube
Also check out Minimal D3D11 pt2, reconfigured for instanced rendering and with a smaller, tighter, simplified overall code structure, or Minimal D3D11 pt3, with shadowmapping + showcasing a range of alternative setup / rendering techniques.