I want to have my Tiger tank on a slight incline, in a tall grass field. With three German infantry running next to it.

How do I make that slight incline?

I would like to replicate the pic below, only on a slight incline.

~Chip

There is the picture.

What you need is to add volume to your base.
For that purpose, you can use styrofoam. You can easily shape it with a knife and glue it to your base. Then you cover it with plaster, wall putty or whatever !
From what I read, there were few hills around the Kursk battle. And they gave a good advantage over the plains around. SO they weere subject of very intense fighting !

That's a great idea, keep us posted !

What Penpen said about the styrofoam.
Your bigger challenge will be making the guys running up/downhill look convincing. Most figures are designed to be placed on flat surfaces. The body positioning of a person running up or down an incline need to be shifted to account for gravity. Take your digital camera and get someone to run on an incline similar to the one you're planning and adjust your figures accordingly. I once saw a really nice dio that was spoiled by a figure designed for a flat suface standing on a sloped surface, that's a battle gravity would have won.