Isometric Pixel Art/Making a Box
Different Methods 
Before we start, let's discuss the different methods of making this box. There are a couple different ways of putting it together:
- The Puzzle Piece Method (Recommended for this Tutorial): Make the separate lines (the x, y, and z axis) and put them together like a puzzle using copy and paste to duplicate the lines. Good for uniformity and if you aren't making different length of your lines.
- The Line by Line Method: Create each line individually. Good if you don't like using copy and paste or if your shape is not uniform (like a person or animal) but is extremely easy to mess up.
- (Not Recommended for this Tutorial)Pixel by Pixel Method: Pros: Makes for really good quality pictures with unparallel uniformity, if done right. Cons: Takes a extremely LONG TIME.
Math? IN ART? 
That's right! We are going to do a quickly lesson in geometry. For your pixel line lengths, I suggest them being multiples of each other (ex: 2 x 2 = 4; 2 x 3 = 6). This makes it look more like a real cube. Also, we must remember that the lines must be of equal length for it to be a real cube. Isometric lengths make this really hard to do, because each axis has a different scale (ex: The X axis (up and down)compared to the Y axis (left to right)are equal, but they are both different from the Z axis (forward and backward)). Eyeball it and find out what looks right to you.
- The "Golden Rule" of Isometric Pixel Art is that for every 2 pixels in the Z axis (front to back) there is one pixel for the X or Y axis (up and down, left and right). Although this may not always work for every single thing you draw isometrically, it is the general rule so remember it!
Let's Begin! 
Congratulations! You've just made your first isometric drawing!