Many years ago my mother and I attended a wonderful 3 day weekend of all sorts of classes offered by the Arkansas Game & Fish. It was called Becoming an Arkansas Woman. Females only! We took classes in campfire cooking using cast iron, canoeing classes, kayaking classes, planting native gardens, bird watching for all different kinds of birds, all sorts of classes. It was held at the 4 H complex at Ferndale outside Little Rock, a beautiful area with a lake, dormitories and a beautiful large auditorium and a modern cafeteria. The last night ended with a banquet featuring wild game, such as pheasant, elk, antelope, deer, and various other game birds. There were all sorts of vendors set up outside the auditorium, and one was a lady selling these leaves of concrete! Hers were painted and finished with a sealer. I bought one, s small leaf, it was a sycamore leaf in light green. I still have it. Mind you, this was at least 20 years ago? Two years afterward I found the instructions in a gardening magazine.
Now when I finally decided to get Internet in 2017, I immediately got hooked on Pinterest and was astonished to see the instructions all over Pinterest! So I will check Pinterest to see if the pins are still there. They even had instructions on how to do the leaves flat and using them for stepping stones.