What type are you looking for?
A flat profile or ? round with full leaves.
A profile one is simple in as much as, you can use a Jogger {1?[30cm]} flat & add cut out profile pieces on the sides, depicting the trees out line profile. They can be joined on using split drop pin hinges or whatever.
The half round takes a wee bit longer for the trunk, unless you make it complete round, using PVC storm/drain pipe or a used carpet roll. Cut a flat base from ply & add a circular or cross brace block of wood, to fit the inside diameter of the pipe/roll, securing on the base & tec screwing the pipe to the mounting block.
Make up the palm branches & leaves from either plastic conduit &/or wire. Make up the leaves using wire coat hangers to reinforce, depending on size, pull over green coloured panti hose. Add calico/muslin rolled strips & paint up. Cut holes in the pipe/roll to accommodate the branches protruding into the pipe. Add calico/muslin pieces to the branch ends, made up on the conduit & to fit wider than the pipe holes. Using either paper mache or the calico, dress up the trunk out line with circular ribs & around the base. Paint to suit.
Similar with the top of the pipe, using a circular cut block of  wood with holes to take the branches.
The branches can be pooped in for set up & removal when storing.
Not really knowing what style of palm you want, I hope this will help!

I made pretty convincing flats by tracing a gobo projection of a palm tree onto lauan.