Ive done a couple of spots where i took the back hoe and dug a hole about 3ft wide x 2 ft deep. Took one of those large plastic tubs like we use for gut buckets put it in the hole and filled it almost to the top with dirt.

I then put my trophy rock and mineral block on it. The minerals that dissolve will stay in the buckets dirt and not leach away. The plastic bucket will last for years when out of UV light and keep everything in one spot.

Have also done this with large plastic flower pots and stump holes.

I buy black or green pots/buckets and don't place them in any low areas where you get a lot of runoff or possible water standing.