If you don't have the option of buying the cake pans, you can try carving them out of the oval or rectangle cakes. You can even print out a huge number 5 and a huge number 0 on an 8.5x11 paper, and use them as a pattern. You can do this by freezing your cakes, and then laying the paper over top of the cakes, poking holes along the printed border to give yourself a guideline for what it's supposed do look like, then carve it out. Frozen cakes are sooo much easier to carve. You can also use the wilton transfer method, which basically means that you use parchment paper like tracing paper, putting it over the design you'd like to copy, trace it with piping gel (make sure to use a fine tip, like tip no. 1) and then flip it over onto your cake and lightly press down along the piping gel to leave a see-through film on your cake that will allow you to see what you're supposed to carve. NOTE: remember to trace your numbers backward (or mirrored) so that when you flip your parchment over onto your cake, you're not cutting out a backwards number 50. Does that make sense? Either method is really rather simple. If you have any questions, feel free to PM me, and I'll try to be more clear. Good luck!