I too use jack stands and for added safety keep the floor jack engaged, if possible. Jack stands have been known to fail too.
As for using wood blocks, if done correctly that method should be as safe or even safer than jack stands. That method has often been used in underground mining to shore up many tons of rock. I’ve used it occasionally in working on my trucks. The way I was taught to use wood blocks was to use layers. Each layer is crossed at 90 degrees to each other and each layer has at least two pieces resting side by side. Ten or 12 inch lengths of 2x4 or 2x6 laid side by side and cris cross at 90 degrees to each previous layer is stable. The method is more time consuming to set up properly, but does work.
