[edit - April 5, 2020]I modified the design to round the corners a bit which keeps the water out of the corners and makes it look nicer. I also added the Fusion 360 f3D file so you can modify this, if you want.

This is a dishrack/drainboard basket. It is designed for a very common rack this is found in many US hardware stores. These racks have a big opening at one end that lets items fall through and back into the sink. Also, the rack only includes a very small basket in the corner.

This rack fits over the last dish support in order to have plenty of width at the base to hold lots of things. It also has two clips at the top that secure it to the rack. Finally, it has a slit at the bottom that lets water drain out without any water pooling at the bottom (the rack is on a drainboard that provides the tilt needed for the draining action).

You will need supports for the two clips, and also for the drain crevice. I printed it right side up, with the clips at the top. This required two towers, one of which came loose during the print, but the the print turned out OK despite that slight failure.

I printed on an Ender-3.

This was designed in Fusion 360 and I've included the f3d file. This is a parameter-drive f3d file so you can do most modifications simply by entering new parameters, rather than editing the model itself.

If I were to print another, I'd round the vertical corners a bit.