Place the template onto a cutting board and top with wax paper.
Place candy melts into a resealable sandwich bag but do not seal. Heat for 60 seconds at 50% power.
Knead the bag and flip over. Repeat and knead the bag until the melting chocolate is melted and smooth.
Seal the bag and snip the tip in the corner.
Pipe the chocolate onto the wax paper, tracing the template design underneath.
Keep the chocolate thick. Top with sprinkles while still wet. Let stand to harden.
Carefully peel the number from the wax paper and flip the number or letter over to the back.
Reheat the bag of chocolate (30 seconds at 50% power) if no longer melted.
Pipe chocolate onto the back and gently press the popsicle stick into the chocolate.
Cover the back of the number with additional chocolate and add sprinkles.
Let the topper stand to harden.
Gently press toppers into the top of the cake.
Notes
I think it's best if you put the stick on off-center. For example, put it on the side vs. the center of the number, so more of the stick is attached to the number.
It might be easier to put wax paper on a cutting board and put the cutting board onto a rimmed baking sheet so that the sprinkles stay on the baking sheet and not all over the counter.
Make sure you keep your chocolate thick and press the sprinkles into the sides as well.