Step 1: The joints
Just cut four cylinders from an old broom handle, length could be about 4 cm.
Then you need a small wood board, at least 1 cm thick.
Make 6 mm holes in both ends of the cylinders, and also on a side of the board.
I've also glued on the bottom side of the board a rectangle of rubber of the right dimensions, to improve the adherence on any surface.
One of the cylinders has two little hole instead of a big one, they're to screw the spotlight holder, so measure the screws stem to find the right diameter. The groove made with a file is not essential, but it keeps the wood far from the hot glass of the lamp.