Align the Y's on your benchtop and position the silver t-tracks as shown above.

 

Each silver t-track is aligned and held in place by special 3d printed plates as follows:

Note: T-nuts should already be pre-slid into the t-track of each Y extrusion, you'll want to position two at each silver t-track position.

 

 

From above, your assembly should now look like this:

 

Now is a great time to take measurements if you'd like to install your MDF bed.  
 

 

Place measurements onto your MDF sheet, drill counter-sunk holes and use the included t-track nuts to secure your MDF bed into position.

You can work on t-tracks or other bed designs later.