I just use a drill press, couple of taps and a dremil. It's fun to try different ideas and put them to the test. Makes it fun to learn that way. DIY will always be there. That's where the best ideas start from.
My first few blocks were cross drilled. They did ok but wasn't the results I was after. Got a better idea using just 3 holes drilled down and using a tapered bit to get a slight tapered base. That worked well. Then I added my own home brewed impingement. That worked even better. Still using it now. The whole block thickness is 1 inches. It's thick but works.
Tried another one with the same idea but to make the block thinner and help increase flow. I mucked up the offset by a few mm.
But it still works, just not as good.
Learned alot doing it the DIY way. From what I learned, I came up with a nice design I like to get milled sometime when I have the extra cash on hand. I have some copper to play with now so I'll have fun with that.