I've read that a trashcan for lxde/pcmanfm is a bit difficult to impliment. Thankfully pcmanfm eventually supported trash however it still does not provide a desktop icon for the trashcan..
To be honest it doesn't bother me. But some that I setup with Lubuntu miss the trashcan so I usually place a desktop icon (trashcan) on the desktop that opens and points to the trash.
It doesn't support drag & drop or right click empty trash but it gives users a reminder to check their trashcan and empty it if necessary from pcmanfm.
Pretty easy. Right click on the desktop and create a new file. Name it Trash.desktop
Then right click on it and open the file with leafpad and copy and paste this in below and save.
I usually name it Check Trash or View Trash. You can name it whatever you want. I try to stick with those names to remind the user to open the trash then empty.
Here is a screenshot....
Hope someone finds it useful.