You don't need a board.
You can solder the LEDs directly to header pins
, or solder wires to header pins, and solder the other end of the wires to the LEDs.
Don't forget current-limiting in series with each LED. When I solder a resistor inline with an LED, I like to insulate the connection and entire resistor with heat shrink tubing, and I like to use clear heat-shrink just in case I forget the resistor is there in the future. I like to insulate all "free floating" solder connections with heat-shrink, including where the wire is soldered to the header pin..
But with 10 LEDs, resistors, and ground wires, you are going to have a mess it you try to "affix" the LEDs direclty to the Arduino. It's better if you can physically mount the LEDs to something else (a front panel, a perfboard, or ...something).