The cradle is the "engine cradle", also known as the subframe up front. There's a nice pad area where the rear bushing of the LCA mounts to. Also can use the notch in the LCA and jack from there.

A simple solution is to cut a 10" or so long section of 4x4 to put the jack on. Back when i had an 8" lift and 37s on my silverado I cut two 10" long pieces of 4x4 and joined them together with a piece of plywood, thereby making a solid "base" that was plenty for using the stock jack under the rear axle or front LCA.