Is it possible for me to create a web page within my site that contains an image and some text that can be accessed by a QR code? It will be just a small image with one line of text giving the date and time. Can I make a web page this small?

Sure no problems

Insert a container to the body

Set the body to
Flex = column
Settings for all = center

In the container insert your image and text

Either give the image a maximum size for however you want it to be
Or the container a maximum width
Set that container also to column

There you are an image with text in the center of your page