Is it draining at all, but just not fully? Does it eventually pump the water out, or is the water just sitting there at the same level no matter what?
Washing machines have a pump under the tub that pumps the dirty water out. These pumps often have a little mesh filter in front of them, sometimes there's also a filter on the outlet where the drain hose ...
The depression you're asking about appears to be simply sloppy manufacturing to me. It doesn't seem like an intentional countersink. If it was you'd probably have flat-head screws instead.
The washer goes under the nut when working with metal, not under the screw head (unless there is no nut or it's an integrated nut).
The screw head should be oriented ...
I take it nothing backs up the floor drain?
I am going to assume this is an older house. The floor drain is probably not hooked up to the sewer line and drains outside to a rock pit or something which is why it doesn't back up.
Perimeter drain that comes into your house with rain / ground water and feed into your sewer service line inside the house would ...
You can use a utility blade to cut through the molding line from below, then when you’ve cut about half of the circle, you can pry the rest of it out without breaking.
Absolutely preposterous that this part ships this way.