Preheat the oven to 120 celsius (250 Fahrenheit) and line a roasting tray with baking paper.
Halve the tomatoes and place in a bowl with the olive oil, garlic, thyme and salt and toss to combine. Place in the roasting tray, cut side facing up, and roast for 1 and a half hours, or until shrivelled and juicy.
Toast the bread and squeeze the garlic out of the skins and spread on the warm toast. Top with the avocado slices, tomatoes and feta. Finish with a drizzle of olive oil.
Notes
The tomatoes can be roasted in large batches in advance and stored in a sealed container in the refrigerator for up to a week. Reheat gently before serving in a microwave or under a grill.