[SlamSlayer]

Theres no fancy app tricks to forced perspective. Its ALL physical placement of the objects you want in the illusion. Unless you just literally want to photoshop yourself and a minifig next to each other. Theres probably apps that can do that. But its not forced perspective at that point lol.

Because the mini fig is so small, you're going to have to get your camera REALLY low to the ground. In fact you'd probably need to get the camera BELOW ground level. So if you're outside, dig a little hole, or find something put the mini fig on that you can get lower than. You're also going to need to stand really far away because of its size.

As for phone settings itself, I'm not familiar with the settings on an Iphone. If you can control the aperture (I know many modern phones can fake this), or depth of field, you're going to need to have the biggest depth of field possible. Which is closing the aperture all the way, setting it to the smallest number. If you can't control the depth of field on your iphone, or your iphone just can't get that deep of a depth of field, you need to do whats called photo stacking.

Photo stacking is where you take a lot of photos (on a tripod) with the focus starting in the foreground and working your way all the way to the background by changing it little by little until you're focusing on the background (and vice versa), and then you combine all the images into one in photoshop or a similar app to create one image where everything is in focus.