Measure the width of the window well at both the front and back where it touches the house.
How to build a basement window well cover.
Start by measuring the well and write the measurements so you can order the plexiglas and metal grate.
You can order them online or buy them at a local store.
Note the widest width.
Try to buy one that comes with a hinge so you can install the hinge and grate.
This well cover will be as small as the door of the well.
It will not take you a lot of time to make such kind of a well cover.
You will not need to have many materials to make this well cover.
Also make sure that the plexiglas will be wide enough to fit over the grate so the metal does not rust and protects the well.
Then measure from the side of the house to the outside edge of the window well in at least two places.
It may be a challenge when you need to expand the size of the egress window well cover.