Ø3 ID Ø5 OD washers.
place shims under the corners, to adjust height to level the bed. Use combinations to get the height correct. Once its level in Y, you should be able to adjust X using Z adjustment.

Print, measure, adjust using appropriate combinations of washers
0.1 Layer height, 0.1 first layer.
If you can't print first layer at 0.1 due to bed not being level enough, you need to adjust your Z heights by hand, in X. It is not so critical that your Y heights are spot on, as it is quite a small print.

I have added another set, to print at outers of the bed, at 1.2mm high.
This is more forgiving of poor setup, you can print at 0.4mm layers, 0.4 start, and you end up with a 1.2mm (+/- that corner's variance from level) washer for each corner of your bed.

In doing this print I found only my back right corner to be out of level, by 0.2mm so I added a 0.2mm shim printed from my first batch, bed is now level!