I drill holes and use acrylic rod which can be purchased/ordered from most local plexiglass suppliers (last year I paid $5 for 6 ft length of 3/8 dia) and I also use cable ties and then use Quickcrete Hydraulic Cement.
The hydraulic cement cures extremely fast (about 5 minutes) so you don't have much time to work with it, so use small amounts. It can be purchased at Home Depot. Sometimes the Hydraulic cement really is enough by itself as it bonds very well. Here's the link to the Hydraulic Cement at Home Depot.
https://www.homedepot.ca/en/home/p.h...000149564.html