In the LEGO Super Mario app, they have created some neat looking bases, however they have a lot of complicated slopes and smooth plates. It's clearly a 3D model, but it looks as though as if it could theoretically be created using available LEGO parts. I can't seem to figure out how to make a slope on a 45 degree angle though. It looks like the base has 65-degree angled slopes which would be totally impossible using available parts, but if you were to build this using 45-degree slopes, you wouldn't want to use 3045 to corner it on the left side, you'd want to use some kind of angled part at the corner. I was curious to know if the following is even possible:
A 45 degree slope doesn't fit the standard geometry of the LEGO system.
The basic "3D module" of the system (a 1x1 plate) is 5 units square by 2 units tall.
A brick is three plates tall - i.e. 5 units square by 6 units tall.
Therefore, the smallest perfect cube you can build is 6 bricks square by 5 bricks tall. It should be clear that can't be split into two "wedges" or "cheese pieces" with 45 degree slopes.
The 2x2 wedge piece in zovits's answer, and all the other 45 degree slope brick parts, work round this by having a small vertical base under the 45 degree sections to make them one brick tall, and therefore they are not stackable to make a smooth 45 degree slope. If you do stack them, the "average slope" is close to 50 degrees, not 45.
At a small scale the part Wedge 2 x 2 (Slope 45 Corner) could do this, but this approach can't be scaled up: