A picnic blanket drink spot that works
Check beneath the fabric before setting down the drink.
Look under the blanket
Move away from roots, stones and holes. A blanket can hide uneven support without correcting it.
Separate sitting and serving
Choose a drink area beside the adult using it, away from feet, bags and food preparation. Keep the entire base on one level supported patch.
Use a table when needed
If the ground compresses or slopes, use a suitable rigid support. A tray on unstable ground still needs its own support check.