Use a mandolin to finely slice the zucchini lengthwise into long ribbons and mix them in a bowl with the 3 tablespoons of olive oil. Season with salt and pepper.
Heat a grill or griddle pan and grill ribbons for approximately 2 minutes each side.
Toss the grilled ribbons with the lemon juice and set aside to cool.
Once cooled, layer the ribbons, garlic and the thyme leaves in a sterilized jar. Top up the jar with olive oil.
Stir the jar to release any air bubbles with a chopstick or skewer.
Make sure the ribbons are completely covered in oil and cover with the lid.