Option 1: Load a GeoJSON file, and create a custom grid (not limited to rectangular)
Option 2: Hold Shift + Drag on map to draw bounding box
Option 3: Enter a centerpoint for your grid, along with a toal area width. This will generate a square grid.
Longitude Latitude Width
Output 1: Cell Size indicates approximate height and width of grid squares. Your grid will contain the bounding box you draw, and may be larger to fit square cells.
Bbox - longitude 1: latitude 1: longitude 2: latitude 2:
Cell Size
Output 2: Cell dimensions generates the number of columns you want, and square grids will be generated to match (distance auto-generated)