How heavy when finished?

I did something very similar. Made them one place then carried to another. I found it very easy to separate the rocks from each other with a screwdriver. I was able to load a bunch of rocks into a garden cart and move them to the other location. I then used the mold to make sure I got the rocks in the right place. If you try to move it as one piece, it might break apart in to individual rocks. I think I used between 64-68 pounds of concrete per mold so the finished concrete will probably weight about that.

You can form the product on the slope preventing the need to move the material after it has hardened. The maximum slope you could place the product on and the recommend base preparation procedure would be similar to that of a standard paver bought at your local home improvement store. When the QUIKRETE® Walk Maker® Building Form-Country Stone Pattern (No. 6921-32) is used it will create individual stones to form the pattern, so if you still intend to create on a flat surface and move, you can move the lesser weight individual stones rather than the entire molded pattern.