At its best:
Place a few crocks in the bottom of the pot for drainage. You could also use broken polystyrene or small plastic plant pots.
Fill the container two-thirds full with peat-free, multi-purpose compost. Break it up as you go to remove air pockets.
Add the 'Tête-à-tête' narcissi to the back of the pot first, followed by the three primulas in a line along the front edge.
Split the ophiopogon into several smaller plants by carefully breaking the root ball apart.
Poke the smaller pieces of ophiopogon between the primulas and narcissi. Fill in with more compost.
Firm down the compost and water the container thoroughly. Check the compost regularly to make sure it doesn't dry out.