Start by painting stripes (vertical or horizontal will work). This doesn’t have to be perfect, it will be covered up later. I was suffering from a migraine when I was doing this which caused me to have very shaky hands and the stripes show it but it really doesn’t matter. So if you don’t have steady hands this might be the perfect thing for you to try.
Then place striping tape in various directions all over the nail.
Go over the entire nail with black nail polish. Carefully remove the striping tape immediately.
The finished result will look something like this: