I made this in the 80s when I had after hours access to the machine shop at the factory I worked at. I cut equal width pieces of oak from main pallet ribs. I used the same stain (Probably Minwax, new color) on all pieces. The color variations were in the wood itself. I cut them to different lengths and arranged them in a "random" pattern with the lightness/darkness alternating that pleased me. I also included the one piece with a gorgeous knot.
The pieces were laid out and glued together on a flat surface. The surface was then finished off with a 36" industrial disk sander, but a good belt sander would work.
The clock cavity was cut out with a router, but could be done with a large paddle bit and a chisel. The clock motor was an ordinary battery powered motor. I've replaced it twice in the thirty years since I made it. I painted the hands white to make them stand out better (especially in weak light). If it were stained a lighter color, black hands could be used for good contrast. Two screws and picture hanging wire are used for wall mounting.