If you don’t want to spend money on a dedicated battle mat, I know some rolls of wrapping paper have 1" square grids (for cutting to specific sizes) printed on the back. Roll out enough to draw the location where the combat takes place on the paper, run the combat, and unroll another clean stretch for the next battle.
I suppose if you were wrapping presents for your party members you could even reuse the wrapping paper on which you drew certain memorable battlefields. “I wrapped this in the battle where Matt jumped off the tower trying to land on the dragon sword-first.”
This actually happened in my group. He’d tied a rope around his ankles and to something on the tower. Two natural 1’s (one for the attack roll, one to determine how well he’d tied the rope) and he spent the rest of the combat climbing back up the tower missing a good chunk of hit points.
