To make the process easy, I would suggest using a bread machine to work the dough. Add 250 ml (just a bit less than 1/2 pint) of tepid water to the bread machine bucket. Alternatively, you can work the dough by hand, kneading for about 10 minutes.
Then, add 45 ml (3 tbs) of extra virgin olive oil.
Weigh 500 g (1.1 lb) of plain flour.
Add the flour to the bread machine bucket.
Add about 8 g (1 level tsp) of salt. Now, knead the dough with the bread machine. Most of the bread machines have a specific program for "kneading". You can also vary the kneading time modifying the program as you wish. I suggest kneading the dough for about 15 minutes.
The final dough should look smooth and elastic.
Wrap the dough into a clingfilm and let the dough to rest for about 40 minutes.
When the 40 minutes has passed, cut the dough in four parts and make four balls (you need two balls for one tray). Take the first ball and using a rolling pin, make a layer as thin as you can and big enough to cover your tray.
Brush the surface of your tray with olive oil and cover it with your first layer. Use a shallow tray, rectangular or circular it doesn't matter. For this focaccia recipe I have used an oven tray 33 cm x 23 cm (13" x 9").
Then, add the cheese to the top of the first layer.
About the cheese. Tradition requires you to use fresh "crescenza" cheese, a white soft cheese which is very popular in Italy. Alternatively, you can try using soft "stracchino" cheese or buffalo mozzarella.
Complete the tray until your cheese is finished. You should have the cheese evenly distributed on all of the surface. For this tray I have used 280 g (10 oz) of "crescenza" cheese.
With the second dough ball prepare another layer that you will use to cover the first layer and the cheese.
If the layers overlap the tray, before sealing the outer border try to cut the excess part.
Then seal by rolling and gently pressing the outer border with your fingers.
This photograph shows the border sealed and the top layer brushed with olive oil.
Also, brush the borders with olive oil.
Now, pinch the top layer with your fingers. You should make holes about 1 cm (3/8") wide.
The tray is ready for the oven.
Meanwhile you have pre-heated the oven at 220 ºC (425ºF). Put the tray on the top shelf and cook for about 20 minutes or until the surface is golden brown and crispy.
Once the focaccia is cooked, sprinkle few drops of olive oil on its top and now enjoy the focaccia with your friends.