Well... A redstone car is really super easy

That’s what you need for a redstone car : (I recommend flat world)
5 x Slime Block
1 x Piston
1 x Sticky Piston

2 x Redstone (Block)


1) Place the slime block in a letter T. (Make sure it is flying one block above the ground)

2) Place the piston in the corner of the T. (It will be facing the slime block that later it will push it)

3) Place the sticky piston at the other corner of the T. (It will be facing the slime block that later it will push it)

4) Place the redstone and it will move.

It should look like this