We have lots of rocks in our backyard, so when we decided we wanted some durable paths to run through the garden, we decided to go with the theme and build a stone path. After doing some research into the cost and difficulty of various options, especially in light of our sloped yard, we figured the easiest and least expensive way would be to use the "Country Stone" Walk Maker, a plastic form roughly 2' x 2'. You pour concrete into it, smooth it off, remove the form, and repeat. It's not really designed to make curved paths with, but it is easy enough to do so by taking the extra precautions described below.

Supplies

We bought the Walkmaker form from our local hardware store, but you can also pick it up online (~$25). You'll need concrete, which I bought pre-mixed by the 30 kg (66 lb) bag. I used a spade to mix the concrete and a 10" triangular trowel to push the concrete into the form and smooth it.

Step 1: Prepare Ground

Good news - all you really have to do here is to remove any grass or other vegetation, and dig down far enough to make the top of the form at the level you want. Because we wanted the path at ground level, this meant just removing 2" (50 mm) of sod. Important piece of preparation work: anywhere you want an intersection, you need a flat area.

If you want a more durable path (e.g. if you're expecting a lot of traffic), dig down further and backfill with gravel.

Step 2: Mix Concrete

I started by mixing concrete by hand in a wheelbarrow, but soon moved to a borrowed concrete mixer after I realized just how many bags I'd need to mix. Your mix should not be runny (or your flagstones will collapse) or too dry (or you'll have ugly air pockets). A shovel load should basically hold its shape when dumped on the mold, but should have no air pockets or cracks in it. In practice, this meant about 3/4 of a one gallon plastic jug of water per 66 lb bag of concrete (3 liters per 30 kg).

Step 3: Place Form and Pour

Put the form at the end of the path, get it level side-to-side, and dump in the concrete (I found it took most of a 66 lb bag per form). Work the concrete in to all of the flagstones using the point of the trowel. I experimented with a rectangular trowel and a stick for screeding the surface, but neither really helped the process and just gave me more to clean. Smooth the top, adding or removing small amounts of concrete as needed. Remove the form (easy provided you cleaned it well after you used it last time!), and very lightly do a final smooth of the formed flagstones.

Step 4: Curved Path

Because you want to curve the path but you don't want wide gaps, you will have to trim the flagstones you just made. Angle the form to the position you want for the next part of the path, and position it such that it marks the flagstones you've already laid. Remove, and using your trowel, cut away the excess. I found it was easiest to do this if you make a sawing motion rather than cut like a knife. Don't worry if there is dirt on the concrete you remove, just set it to one side and it can go in the bottom of the next mold. Put the mold back down, and repeat the process. You'll find a gently curving path looks much more interesting than a straight one, and well worth the extra work.

On Quickcrete's website, they show someone using the form itself to slice off the corner, but in my hands at least this just made a mess. I suspect they're either being disingenuous or they were using concrete with no (or very fine) aggregate. Pushing the form down through wet concrete squashes what you've already made and traps concrete under the form, making it hard to get the level for the second section correct.

Step 5: Intersections & Finishing for the Day

The reason T-junctions (and crossings) need to be flat is because paths that slope up and down are fine to walk on, but those that lean to one side are not. And you can only achieve that in all directions if your intersections are level. So factor that into your planning.

I found that it took about 20-30 minutes per form, including the time to mix the concrete as I went along. You could definitely speed this up if you had help. I generally did 6-8 bags of concrete in one stint (2-4 hours work), after which I needed a drink and a lie down. BUT when you finish off for the day, be sure to do the trimming of the flagstones in preparation to lay the next one! Otherwise you will either be forced to lay it straight OR do some creative sculpting of the flagstones by hand. Much easier to just pre-trim them.

Got a little left-over concrete? Find some bare ground and make some more flagstones. You can use them as individual pieces to widen the path in places, or to broaden the intersections.

Step 6: Fill Gaps

We filled the gaps with sand, which does a nice job of locking the flagstones in place. We plan to encourage moss to grow on and between them. The path serves to provide a mud-free walkway that confines the garden on one side and the lawn on the other, and at the back of our property goes into the garden to allow easy maintenance of the plantings on both sides.