You prepare a corpse and bind it to your will.  Choose a corpse of Medium or Small humanoid that has not been dead longer than 72 hrs at the completion.

Upon completion, the corpse becomes an undead mummy as found in the monster manual. However, if the corpse is of a small humanoid, replace the medium size of the mummy with small and replace its movement speed 20ft with 15ft.

As a bonus action on each of your turns, you can mentally command any mummy you animated with this spell so long as the the creature is within 100 feet of you. The mummy knows any language it knew in life and will obey any verbal commands you give so long as it can hear you and understand the language you use. You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor. If you issue no commands, the creature only defends itself against hostile creatures. Once given an order, the creature continues to follow it until its task is complete.

The creature is under your control for 1 year, after which it stops obeying any command you have given it. If you die before the spell is ended it continues to fulfill your last orders to the best of its ability until it is destroyed or the duration ends.

At Higher Levels. When you cast this spell using a 7th-level spell slot, the mummy obeys for a decade. When you cast this spell using an 8th-level spell slot, the Mummy obeys for a century. When you cast this spell using a 9th-level spell slot, the mummy obeys your orders forever.