I finished the little sidewalk leading to the gazebo structure, then created a little bed of mulch next to it to better display the good ol' papercrete hand -- one of my first efforts in papercrete and holding up very well.
Then I set my "faces stepping stones" in mortar on either side of the walkway, and finally, after adding some fence and pieces of rebar, poured the slab.
So far the difficulty with modeling in concrete (sans paper) is moisture.
Very tricky, at best. A hair too much water turns a sand and cement mixture to mush. Then I'm back to adding more sand and cement, trying to firm things up. So far, the best way to mix "concrete modeling clay" is in very small quantities by (rubber gloved) hand. Adding joint compound to the damp, crumbly mix of sand, cement and water makes a soft, sticky "clay" that is still not ideal and makes detail difficult. Even moisture left on the gloves from washing off after mixing will quickly absorb into the mix. I learned to keep a towel on hand for after rinsing. Another turning point came when I left the mixture to cure for awhile -- maybe an hour-- which firmed it up a bit.
All of this is much easier when cellulose fiber (paper insulation) is added, which I didn't want to do for the sidewalk. I'm researching it -- trying to find a better recipe.