Yes, most materials either don’t arrive perfectly flat, or can absorb moisture and warp a bit… So these are a fabulous free design:
hold down pins
Also magnets can be great for thinner material (though don’t get super strong ones or too close to the path of the beam, as the magnetic field can affect the beam itself).
When the material doesn’t contact the bed tightly, the gaps will not only cause more flash/scorching, but can lead to incomplete cut-through. If you’re in a high humidty season/area, you’ll want to slow down your speed a bit to compensate for that, too.
I don’t work with wood myself (apart from a sign or display board), but there are loads of others who do, and may have already posted great storage ideas as well as settings for different species, too.