Jack platform?

I have a gravel driveway and some issues with my floor jack (not)rolling as I lift a car. I've been using a leftover particleboard book shelf but after 3 uses it falls apart. I'm thinking a 2x12 would work nicely, but I wonder if pine would hold up or if I need to go up to a hard wood?

3/4 inch plywood has worked well for me in the past. I like it better than dimensional wood.
Edit to add that sometimes you need to get the car part way up, set it on a jack stand, reposition the jack, and then go the rest of the way. This is just part of working on gravel.

T111 exterior wood works well for this purpose, just keep the smooth side up.

I have two nice 2X10s about four and six feet in length, I use one for the jack and the second for the stands (stable) and I have a section of 3/4" plywood I use for lower cars.

Paul

I use a 2x3 piece of 3/4 Plywood for my jack and 1x1 squares for my jackstands.

2' of large metal channel scrap works great too.

I also have a couple sets of cheap jack stands with the bases welded to chunks of 1/4" plate so they don't sink in the gravel or dirt.

Another vote for plywood, it's what I use.

We use plywood at the track

I've got some 1/4" thick fiberglass panels that I use. Work really well, plus thinner and lighter than wood. Also great to keep stands from sinking into dirt/asphalt. Probably more expensive to make though.

Had a gravel/dirt drive for 25 years. Instead of fighting it I worked with it. Place jack and pump it up enough to let the jack sink into the gravel preventing it from moving. Then release anything preventing the car from rolling. Pump up jack allowing the car to roll while jacking. Then chock, set park brake, auto in park/manual in gear, or whatever necessary to keep it from moving. Jackstands on boards or wheel cribs before work is done under car. When you let it down reverse procedure to allow vehicle to roll while lowering.

This method is particularly useful when working on lowered cars when a board under a jack makes the jack sit too high to fit under the car.

Maybe pour a concrete pad large enough for working on the car?