A tool that helps building a ‘trailway’ on a slope: San Angelo bar. You mark where the cut ‘in’ on the slope will be for the trailway and you drive the tip (spade or pointed) in at that point and then pull the top end of the bar towards the down slope. Watch your toes, the bar is heavy. Drive the tip of the bar in by lifting the bar (2 to 3 feet) with the tip down and then dropping the bar (tip end down), even help gravity by driving it down instead of just letting gravity do the work.
The San Angelo bar is also useful if you need to remove cactus, particularly yuccas. It is also useful when trying to dig in compacted or rocky soil.
I used to do trail maintenance in Los Padres and San Gabriels. The San Angelo bar was my favorite ‘weapon’. Good for moving rocks too.
I wouldn’t use the bag of cement method. You end up wasting a lot of cement. You only need just under 2″ thick and a bag of cement is much thicker. The other problem is that it will be hard to get the entire contents of the bag wet. Odds will be that it will harden with the center still ‘powder’.
You can use cinderbrick for the ‘retaining wall’. Fill the holes with dirt and put plants in them (holes upwards). You can also use cinderbrick for the steps by putting them sideways (holes horizontal) or oriented normally.
Another trick would be to get all of the loose rock that you don’t want and to press/work them into the loose soil of the trailway after you cut it into the slope (don’t use the smooth surface rock though because it would be slippery if moist)
Another option for retaining wall is interlocking brick (some places mix this up with pavers, but it is for vertical walls).
