I just used a tube of construction adhesive from the local big-box hardware store, nothing special. The cinderblocks were construction scrap collected by my pack rat landlord, so they were just hanging around for free already.
The plywood wedge was something I built a couple of years ago for an ETX-70, a much lighter scope. But, my dad always taught me to overbuild everything and so I made this out of three-quarter inch cabinet grade plywood and hardware that was well more than enough for the job for that little Meade telescope.
Fast forward to now, I had the Evolution mount and the six-inch imaging Newtonian that I wanted to try on a cinderblock pier. I figured I wanted to make a bigger wedge than the one I used for the ETX-70, but in the meantime, I thought that little wedge would be good enough to at least be a proof of concept for the larger rig. Turns out that it worked, and continues to work, so well that I don't think I'm ever going to build that larger wedge. I carefully polar aligned it two months ago and have done at least two dozen sessions on it since (including a number of them live streamed – see the live streams thread in the EAA section here on Cloudy Nights) and it is just rock solid.
I will probably get out there at some point during the next couple of weeks when the moon is in the sky and I normally do maintenance type things anyway, and check the polar alignment using the SharpCap polar alignment tool. I don't expect to see that it has changed much, if at all in that time.
It's working far better than I even hoped!
And if there is any threat of liquid sunshine coming my way, I just bungee cord a trash bag over the top and it's all good. Simple and easy.