Ok , so recessed panelling this is what this type of trim treatment is , because the centers are recessed . I have simply taken the wall and added MDF to it , really it is that easy ,most of the joints are butt joints, again easy .
I first removed the trim that was existing and replaced the baseboard with a flat baseboard of MDF , 5 1/2 inches wide. I then determine the height { I installed mine at 44 inches } and draw that around the room with either a laser level or a regular level. I then mark out were the vertical pieces will go and evenly space them out and trace their locations . They do not have to be exact same space on each wall as walls are all different widths , so it is done to visually be pleasing.
I then attach the top piece which is at least 4 inches wide but if I were to do it again I would do little larger maybe even 5 1/2 inch because the chair rail shrinks the look of the top piece and I like it too be a good width, the vertical pieces are 3 1/2 wide. I them took a trim piece of chair rail and attached it to the top of the top rail , then place in all of the vertical pieces , it is really that easy . I did use some latex adhesive which is a helpful item, then I used nails to secure all trim . After this stage I then use latex caulking to fill in where the wall meets the wood and all joint seams, for a clean finish . Lastly I painted with 3 coats of white {your choice} in a semi gloss . I finished the baseboard with a sunstantial 1/4 round piece of trim .
Oh I should mention , I always countersink the nails and fill them with nail filler and sand them before painting , nothing looks worse than nails showing to ruin your hard work.
