If you can select your material so that the face grain is vertical,you can likely hide the joint line.
Custard mentioned selecting riftsawn material for legs before,
as it leaves a vertical grain line in two dimensions.
An interesting post which you can likely find easily enough.
Not ever looked into much design of beds, but from the ones I have dismantled,
they have had angle iron frames attaching to hefty cast iron brackets,
and assembled with coachscrews into hefty headboard legs and footboard legs.
I presume you may need some angle bits to stop those legs racking at the least, as the drawing appears quite slimline to me.