I like harder wood but anything will work, I have made them out of walnut, cherry and osage because I have a lot of each.
The ball thickness will determine the board thickness, I like mine at or near the ball diameter, I start the balls in the block with a ball starter and have the ball slightly protruding out the other side.
Here is a drill chart for each caliber, you don't have to have a 35/64 bit to make a .54 block, I suspect you could use a 1/2" bit and sand the openings to fit.
I have a lot of .54s so I bought the 35/64 bit, even with the bit you may have to sand the hole to enlarge it a little to fit your choice of patch and ball in the hole
I’ve made a few and the chart diameters did not work for me, holes ended up larger. I used some scrap Oak flooring and it worked well. I want to make some more and get a little fancy with the boards. My first ones were straight boards and while they work fine are not very artistic. Good luck.