I learned this on another forum. Inexpensive, easy to build, and all parts can be purchased at any hardware or home improvement store.
This was my first build. I used 1½" PVC for all of the main parts except the crossmember pipe used for stability.
This is my second build. Also used 1½" PVC for all parts.
Here's how it the second one looks when it's mounted.
If you don't have a PVC cutter, a hacksaw works just fine. After you cut with a hacksaw, use sandpaper to smooth the cut edges. After you get everything cut, put it together without PVC glue and place on your yak to see what adjustments are needed. Glue it together after you've made the adjustments. I spray painted them after the adjustments and gluing were complete.