Short answer stupid, considering current technology and knowledge.

long answer- First we need to create a core of metal which rotates and creates a lot of heat and energy which does not cool down rapidly. Too fast or too slow rotation will not support the creation of magnetic field to protect planet from outer radiation and mantle followed by crust where life could be a possibility. Suppose we achieved all those things. Here come a tough part.

Once the crust is created we need to also carefull design how tectonic plates are placed, where we need to give escape vents for lava to disperse as excess energy. Deep valleys for oceans. We need mountains, rivers, valleys etc (no deserts pls). For different types of life. We need to carefully design the axis, speed and tilt of rotation of the planet, for which we need a mechanism which can control core of planet from outside.

A viable atmosphere which can have exact atmospheric pressure, power to block radiations, meteors and other objects.

These things are random and rarest of rare occurrences in universe. so humans cannot create planets. Because to create a planet we need to be capable to creating the very foundation of these things. We need to create a new physics, chemistry and biology for new planet.