This idea probably came from Pinterest and I thank whoever came up with the idea. This holder is quite simple but does require some power tools.
Planer (or not depending on the size of your block)
1-1/2" spade bit (1-5/8" is better but is harder to find)
3/8" drill bit
Wood block (mine is 2-1/4" x 2-1/4" x 9-3/4" of a soft wood)
Varnish etc. to finish
1) Determine the length of your block based on the number of tealights you will use. I used four lights and left 3/4" at the ends and between the 1-1/2" holes. Locate the centerline of the block and measure to determine the center of each hole. Use the 1-1/2" bit to drill holes 1-1/2" deep.
2) Set the tablesaw blade at a 20 degree angle so it only extends 7/8" above the table. Use a scrap piece of wood to determine where to place the fence for the first cut. My first (lowest) cut is 1/2" from the bottom of the block. When you are sure of the fence location, make the first cut. Flip the block to make the cut on the other side. Move the fence over 3/8" and make a test cut in the scrap piece of wood. Adjust the fence as needed. Make the second pair of cuts on the block. Repeat the process for the third and fourth cuts.
3) Use the 3/8" bit to drill a hole through the center of each 1-1/2" hole. This hole is for removing the aluminum tealight cup from the hole using a pencil.
4) Sand off the rough edges of the block and each of the side cuts.
5) Sign and date your project.
6) Apply a finish to your project.
7) Insert tealights into the holder and enjoy their soft glow on a dark night.