The simulacrum spell says:
If the simulacrum is damaged, you can repair it in an alchemical laboratory, using rare herbs and minerals worth 100 gp per hit point it regains.
What else is needed besides the rare herbs and minerals?
The term "alchemical laboratory" implies a room filled with…stuff, but the spell doesn't say what that stuff is. Clearly the GM will need to interpret, but is there any other guidance that might inform that interpretation?
Possibly relevant, previous versions of the spell were worded differently. For instance, the AD&D 2e version of simulacrum said:
Damage to the simulacrum can be repaired by a complex process requiring at least one day, 100 gp per hit point, and a fully equipped laboratory.
Maybe that means the intent is that the current version required a "fully equipped" laboratory, or maybe it means the opposite.
Best Answer
There's no guidance, ask your DM.
If you search the rules for alchemical laboratory you'll find the only reference to it is in the text of Simulacrum.
However there are some examples of alchemical laboratories in adventures that may serve as inspiration.