Best way to approach 2d level design

Im currently designing levels in blender for my 2d side scrolling gamein Unity3D. Its not techniquely 2d because the levels will have depth but movement is only on a x,y plane. Given that, im not sure how to approach creating these block style levels… I know one way would be to have one single cube and extrude it multiple times to the desired layout, but im not sure if this is the best way to go about it. Should i create a bunch of separate cubes and place them all in the proper position? Here is an image of an example level that i will have to design.

Im very new to blender and im not sure how to go about a simple project like this. Any help is appreciated!

I think you can use planes to do this, I saw a guy developing a side scrolling game and he just used planes

Well the thing is its not actually 2d. Its 3d in the sense that theres depth to the view of the level but movement is only on a x,y plane. Using planes i believe would not give the object any depth. Im pretty sure i will need to be utilizing cubes but im not sure how to go about forming them to the shape of the map.