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Anthony N.Your best bet is an indirect, open light source. The shady side of a house, the garage with the door open, etc.
Try and zoom the lens to the longest (telephoto) focal length, even if it means standing on a chair or ladder. This will minimize distortion and keep you far enough away that hopefully you won't reflect in the card or slab. Be sure to get as close to straight over the object as possible to minimize distortion (aka keystoning). Note that this might (depending on your camera settings) give you a slight blue cast. If your camera has a setting for a cloudy day set it to that, it should clear up the color shift. Alternately if you have photoshop it's a 2 second fix to color correct
Alternately you can set up a basic copy setup- a light on either side of the subject at 45 degrees. Home Depot worklights work well for this, and are bright enough that you probably won't need a tripod.
Remember control of highlights and hotspots are a lot like playing pool- if you are at the same angle to the subject that the light is you're going to see the light in the reflection. Since you need to be straight on to the item you want to move the light at an angle to it for even illumination.
If you'd like more specific info feel free to email me at the address on my sign in.