You can create Tracks in ModNation Racers easy! You can create a Track a found in Creation Station.
Creating a Track Edit
To create a Track, go to the creation station ( unless you just went in Creation Station when you started up the game). Then find the the table with all kinds of Track Props on it and press X. You will see the circle menu. Select the New Track, then pick a theme
Start up the new Track Edit
You will once again see the circle menu, with three options:
Controll the Elements
Lay Track Edit
Select this and you will see your mod and kart appear on the screen. Drive around the terrain to find the perfect place to start the track. Press X once you found one. then you will be in a steamroller. Use it to lay a track.