Can you lock the focal length on a zoom lens like the Sony SELP1650?

A zoom lock included in the design of a lens was more common back 30-40 years ago than it is today.

And although you might consider suggesting duct tape snarky, you're not too far off from what many experienced photographers use today when they wish to keep a zoom lens at a specific setting for a series of photos: gaffer's tape. It holds well enough but doesn't leave any residue once removed.

There are several other methods involving wide rubber bands. There's even a company that makes them and specifically markets for this use: lens bands. Most such bands aren't much different from the wrist bands that have become popular for showing support for various causes. Depending on the size of your lens, one of the wrist bands might fit the bill. I have a rubber wristband on my very well used EF 24-105mm f/4 L IS to prevent zoom creep.

You can also find a plethora of DIY methods by searching the internet for "fix zoom creep". Some of these methods are lens specific. Including the lens name in your search will help find those specific to your model lens.