Find a hard wood chair or bench. Sit bolt upright on it, with shoulders back and down. Suck in your abs and tuck your pelvis under just a little bit so that you are firmly planted on your sitbones. Now lean forward.

That's pretty close to the position.

Once you transfer that to the bicycle, you should also put some weight on your feet so that your sitbones are more or less "perching" on the saddle.

This requires good core strength to maintain for any length of time, but if you've got the good core strength, it's possible to maintain it for hours and hours quite comfortably.