Your continent is Africa
At the scale you mentioned, I measure the overall size of the continent (including the smaller sub-continent) at 6250 by 6000 km. Africa is slightly larger at 7900 by 7300 km. The sub-continent I measure at 2500 by 1500 km; this is about the same size as Morocco and Algeria, at 2500 by 1900 km.
I propose that you model your continent after Africa, which is all formed on one tectonic plate. As you see from the elevation map, it isn't too far fetched to imagine with slightly higher sea levels that the upland areas of Morocco and Algeria in the far northwest could be separated into a smaller sub-continent off the coast.
Africa has plenty of tall mountain ranges, formed by the volcanic action of the Great Rift Valley. There are volcanic mountain ranges like the Tibetsi and Cameroon line. Most of southern Africa is a high, flat plateau; the center in Congo is a sunken basin, punctuated by a mighty scar where the basin's rainforest unleashed its waters on the Atlantic.
Look up stuff on Africa, and make your continent look like that.