Chassis Construction

Red = outline credit card (it will be 54 x 86 mm)
Black continuous = cut (lines) and drill (holes)
Black dotted = fold (see tip 2 below)
Green dotted = glue c-parts here (chassis reinforcement) with superglue
Blue dotted = centre line of the card

Tips:

Draw the lines on the card with a waterproof marker.
Hold the sharp edge of a hot (by flame) hobby knife slightly above the dotted line and bent the flap 90 degrees upwards. Then let it cool down.
Dimensions and positions of axle holes, guide pick-up point, hole d and c-parts, depends on the hardware you're going to use. For the axle I used Slot.it hardware, Starter Kit 01 (axle, crown wheel, wheels. The included bearings I did not use, the wear resistance of the plastic is amazing!). Slot.it tires too. For the guide I took a standard Parma unit.
Most important: position the motor on the centre line and glue with superglue. The axle (with the crown wheel) has to be on the same level as the centre of the pinion. That will define the height of the holes in a.
If the holes are (accidentally) to big? No sweat, just glue small pieces of card in the right position to locate the axle properly.

All done? Then you will have fabricated something like this:

Note: The chassis doesn't necessarily need a front axle to perform well, so I think it's up to the builder to incorporate one or not. If not, forget construction of the b-parts. In that case one could build and attach a kind of high downforce wing car body.