I had a Pathfinder dry-erase foldable grid but hated it because it didn't lay flat.
I've variously used:
Nothing but minis on a table and a foot-long ruler to measure movement and distance.
My own 1" grid on 8 1/2 x 11 inch paper (the grid itself is 8"x10"). If I need more space I can lay more pages on the table.
The above but one of the players actually draws the room on the paper. I often have a very small scale, maybe 1"=20 feet, map that I've printed from a pdf of the module that I can cut out with scissors and construct the dungeon as we go. If the small scale map is already visible, one player can draw the battle map while I get monster tokens, roll initiative, etc.
Pre-printed 1"=5 ft maps from available pdfs. With so many old adventures available in legal pdfs, I can crop an image of the map out and then resize it as needed. Then print it out and waste lots of paper! I print on low quality as the paler color actually works well to not be too prominent. A pair of scissors, some tape, and a pencil to mark the back with the room number and I'm good to go! Sure beats hand drawing on home-made grid paper like I did 30 years ago.