Use a 25-30cm pots
Plant the bottom layer of bulbs (Tulips) on 5cm of compost so they are approx 15-18 cm from the top (pointy ends upwards) and ensure they are not touching.
Cover with 5cm of compost before planting the next layer (Daffodils) in the same way so they are approx 10-12cm from the top don’t worry about if the bulbs are sitting over the lower layer of bulbs, they will find a way through
Cover with 5cm of compost before planting the final layer (Crocus) intersperse the two types and plant so they are approx. 5-8cm from the finished soil level
Finally cover with compost and leave outside over winter and wait till spring.
Place the pot on feet so it can drain and prevent bulbs rotting.