One of the techniques you can use with Excel to make a presentation look better is to assign an outside border to a cell or group of cells to call subtle attention to them.

Selected cells in an Excel spreadsheet can be emphasized by adding a border to make them stand out. For instance, you might wish to call attention to the result of a calculation. Borders can be ...

In Excel you can put borders around squares and they can be changed by going to Format, Cells, then Borders. However, this is very long-winded when not every cell is bordered.