How to make a Roman shield with cardboard

The Roman shield (scutum) was a type of shield used among Italic peoples in antiquity, and then by the army of ancient Rome starting about the fourth century BC. The Romans adopted it when they switched from the military formation of the hoplite phalanx of the Greeks to the formation with maniples.

The Roman republican scutum lasted from the 4th century to the 1st century BC, when it changed from an oval shape to a rectangle shape, the one that all of us know from the movies.

This is a Roman republican scutum.The scutum was a 10-kilogram (22 lb) large rectangle curved shield made from three sheets of wood glued together and covered with canvas and leather, usually with a spindle shaped boss along the vertical length of the shield. The best surviving example, from Dura-Europos in Syria, was 105.5 centimetres (41.5 in) high, 41 centimetres (16 in) across, and 30 centimetres (12 in) deep (due to its semicylindrical nature), with a thickness of 5-6mm., some source prove it weighed about 5.8 kg (13 pounds) to 6.8 kg (15 pounds).

Measures I used are:
120 cm length and 55 cm width.