Is there a blank label template

Need to create multiple labels for my wife to label the contents of her kitchen storage jars.
Can’t find a way of:
Creating a label with size dimensions (height and width) and text (say) centred in the middle.

I use LibreOffice on Linux Mint, so this answer may not be exactly what you need…

There are hundreds of pre-defined labels for you to use in Writer under menu selections: File->New->Labels.

This should bring up a Labels dialog box where you can enter and adjust for almost any labeling situation you need. See the LibreOffice help page online click here or, if it’s available, in your own installation. This will help you understand what all the options can do.

Centering the text in the label is not part of the label creation, but can be done in the document produced by the label dialog. There is an interesting article on “fancy” labels click link here that may help you modify labels created.