First you need to create a cloning machine, you can get it using the recipe as in the picture below or by entering the command / give @s vc: cloner
After you have created a cloning machine, place it on top of the block you want to clone.
Next, put coal in the car and it will start the cloning process, which will take about 16 seconds. After this time has elapsed, you will have a ready-made block.
After creating a block, the machine will take 20 seconds to cool down and after this time you can start cloning a new block.