"Bore dydd Llun"
I'm just starting out, but I think it's an aspirated L sound. So you'd put your mouth in an L position, then blow out like an H.
If one thing bothers me about welsh, it's that I don't know if I'm saying 'Li' right.
The sound for ll is /ɬ/. Put your tongue in the position for an L, and breath down the sides of your tongue to make a hissing sound.
More a thing for anyone reading through this page in future, that's for sure.
I thought, dydd was dropped, same as Saturday night be Nos Sadwrn, and not Nos dydd Sadwrn
well i thought that nos da noises but it was night but any ways nether mind that its just welsh is a little trickey :)