Lay the wire flat directly over the soil after you finish planting and pin it down with U shaped garden staples every foot or so, pushing them in firmly. The wire acts like a lid, so squirrels cannot dig through it, but the shoots can still grow up through the gaps in spring.
For extra protection, you can cover the wire with a thin layer of mulch or leaves. It makes the bed look natural, and squirrels lose interest when they cannot see or smell freshly turned soil.
What about spring?
When the first green shoots start to push up in early spring, you can either leave the wire in place and let them grow through it, or lift the wire off once the shoots are a couple of inches tall. If the leaves grow through the holes and you want to remove it later, just cut the wire in sections and pull it out carefully.
Other things you can try
Some gardeners swear by planting daffodils, alliums or hyacinths along with tulips, because squirrels tend to leave them alone. Daffodil bulbs are toxic to most animals, so they rarely get touched. Mixing a border of daffodils around your tulip bed can help keep things safer.
Sprays and cayenne pepper get recommended a lot, but they wash away with the first heavy rain and need to be reapplied, so they work better as a backup than as the main plan.
Plant late, bury them deep, keep the surface clean and pin down a sheet of wire. It takes maybe twenty extra minutes, and next April you will be looking at a bed full of red and yellow tulips instead of a bed full of holes.
