I made a copy of the last one shown in the link. Using it for over ten years on two Valks.
The big flat board that goes between the jack and the engine does not need to be 2 X 4s, one inch stock is fine. It can be a little troublesome getting the jack AND the home made adapter under the bike while on the kickstand, so the one inch board is easier to slip into place than 2 X 4s. Still, the trick that works best for me is to stick a small 2 X 4 under the kickstand (centering up the bike more), before shoving the jack and adapter under the bike.
Just remember that having the bike on level ground when using the jack is a good idea.
I don't strap my bike down either, though if I will be pulling big wrenches or doing any extended work, I put one jack stand under one front engine guard (then let the jack down so that jack stand is solidly captured on that engine guard). If you don't do this, and drop the rear wheel, final drive and shaft, the bike quickly gets real light in back, and want's to tip forward off the jack..... more excitement than you want.