How do I make a template for wine bottle labels?

Find one you like, measure the size, set up the custom size in Page Setup, or make multiple labels on a full A4 or letter size sheet then add the usual content on it.

It is only a rectangle with text and pictures on it.

Peter

Do a google search for: image wine labels.

Here is one that I just made with Pages v5.2.2 using a shape filled with a texture, two images layered on top, and three text boxes (using Placeholder text) layered on top of the shapes and images.

There are many common size label templates for wine bottles on the net, you can find them here If you using a graphic editor, you can use the PDF templates as a guideline layer. Otherwise open the Word template and insert images and text into each label cell.