How can I make too-small interior shutters work for my window?

You could add boards like 1 by 3/4 to each side by gluing on with gorilla glue and clamp to set. (For glue to dry) Check your measurements may be able to just add to one side on each shutter.

We had a similar problem and we built up the sides of the window frame and attached the hinges there. See our post about it: https://www.frugalfamilytimes.com/2018/11/how-to-make-small-basement-window-look-bigger.html :)

take shutters apart removing hinges. add boards same thickness & length of shutters to each of the eight sides. lay the shutters on floor measure the window opening & shutters to determine how wide you need boards to be to have shutters closed. add boards onto shutter sides with construction adhesive and long screws paint them color you want then put hinges back on and rehang them on window frame.

Thanks

Hi Karen, hope this helps you out.

You could mount them so they meet in the middle, and just put some cute curtains at each side to cover the gaps, you will never have to close the curtains but they would cover the area the shutters are not covering on each side

If you ran some type of wood slats you could then attach the shutters to that but that depends on how much the shutters are off from the size of the window.