Repairing 1930's Fireplace Hearth

[newbiedoobiedoo]

I'll preface this with a disclaimer that I am a total beginner and have almost no knowledge, so any help you can provide would be greatly greatly appreciated.

I recently moved into a 1930's house and would like to repair one of the hearths. The previous owners placed marble slab over the original tile and when I removed the marble, the tiles were damaged beyond salvage (surface was pockmarked/marred by whatever adhesive they used to hold down the marble).
I removed the old damaged tiles and as I was doing this, found a thick mortar bed underneath (up to 5" thick at its deepest). Most of the mortar bed was too crumbly to salvage so I removed as much as possible. The mortar seems to have been placed directly on the wood baseboards in the middle of the hearth and there is a fairly solid pads (?mortar) on the two sides that I left alone (see photo). Now the question is, what's the best way to fill the hole? Should I just replace the mortar directly onto the wood and existing pads on the side? There is also a gas line for the fireplace log lighter that was until recently encased in mortar. Should I just encase it in mortar again or is there something else I should do with it? Then I assume once I have a nice level bed, I can just tile over it. Would you recommend doing a mortar bed and laying the tile into the bed or letting it dry and using thinset to adhere the tiles? or soemthing else altogether.

Again, please excuse my lack of knowledge, thanks in advance for your help!

[Davy]

I would sweep or vacuum the wood, staple tar paper or plastic (lay down a trash bag) over it. Then staple lath down over it. Back in the old days, they would slap the mud down right over the wood. You might can do that again but it's just not a habit I have. You want deck mud (dry pack). It's easier to form and shape than soupy wall mud or concrete. Floor and Decor has 4 to 1 deck mud that works fairly well although I usually mix it from scratch using 5 all purpose sand to 1 portland cement. Mix it dry first then add just enough water to get it to cling together. About the consistency and the amount of water you'd need in beach sand if you wanted to build a sand castle. You'll find more info in the "Liberry" about deck mud.