Can I build my own ARM board like the raspberry pi

If you are asking then the answer is almost certainly no, not at the moment anyway. There are lots of enthusiasts who would have no problem with that but there is a learning curve and you have to be willing to see some ruined boards. The signals between the chip and memory have quite exacting requirements, an ARM Cortex-M chip is much easier to deal with.at home.

In the future this may become much easier, there are machines coming out that will produce a board using 3D printing techniques so one could produce complex multilayer boards at home. This is about the level for home users at the moment though.

3D Printing: 3D Print A Solderless Circuit Board

If you are asking then the answer is almost certainly no, not at the moment anyway. There are lots of enthusiasts who would have no problem with that but there is a learning curve and you have to be willing to see some ruined boards. The signals between the chip and memory have quite exacting requirements, an ARM Cortex-M chip is much easier to deal with.at home.

In the future this may become much easier, there are machines coming out that will produce a board using 3D printing techniques so one could produce complex multilayer boards at home. This is about the level for home users at the moment though.

3D Printing: 3D Print A Solderless Circuit Board