I have been using the heavy plastic "Trailer-Aid tandem tire changing ramp." I use it mostly for raising one wheel at a time to adjust the brakes
. Last summer, I also got to use it to change two tires
that blew out. It went very smoothly. I was amazed that my senior memory remembered from years ago to loosen the wheel nuts before raising the flat tire off the ground.
The Trailer-Aid worked great as a jack, both on an asphalt road or shoulder, and on a firm dirt shoulder. What I like about it, compared with the Blaylock or Anderson Jack, is that it has an indentation for the good tire to settle into stably, and I can feel it from the tow vehicle, so I'm not depending so much on the tow-vehicle parking brake or the wheel chocks on the other side of the trailer to prevent the trailer from rolling off the jack while I'm working on it. That's especially important for brake adjustment, when I'm underneath the trailer.
I also have a pair of Anderson levelers, which look a lot like the Anderson or Blaylock jacks. A pair of those under both tires
on one side of the trailer are an easy way to level side to side, usually. Only on deep sand or pebbles do they just push down in or slide forward without leveling. After leveling, an extra pair of supplied small wheel chocks effectively lock the levelers so there is no tendency to roll off of them.