foundation for stone veneered planter box

I want to build planters in front of my house. What would be the proper foundation on which to place concrete block to which I will veneer the face with stone? Should rebar be used? If so how deep? Any type of sand or other substance as a base for the block??
Thanks in advance for any input.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.