As with nearly all these fingernail flies, which I have used to create a range of patterns, you can prepare the fingernails in advance for the pattern you wish to dress.
Take the fingernail of the size required, and trace the outline on a piece of flat closed cell foam. I have used white here, but you can use any colour you like;
Now take a smaller fingernail, trace the outline again, and cut it out;
Take your fingernail, and using contact adhesive, ( I have used UHU here) or super glue, or whatever else you have available, glue the large piece to the fingernail.When set, glue the small piece on as well;
Allow to set thoroughly. You may prepare a number of these bodies in advance, and allow them to set. You should end up with something like this;