How do I set up a vertically split terminal for the vim-slime plugin?

For the vim-slime plugin, these are my settings:

let g:slime_target = "vimterminal"
let g:slime_paste_file = "$HOME/.slime_paste"
let g:slime_vimterminal_cmd = "sbcl --noinform --load " . @%
let g:slime_vimterminal_config = {"term_opencmd": "vert term | buffer %d", "term_finish": "close"}

What I wish to do is to have my terminal vertically split upon opening. Currently, it splits my terminal horizontally. I did some research and found out that I can manipulate these settings for slime_vimterminal_config. My idea is to run vert term and pipe that to my screen buffer, as seen above. This is still not splitting my screen vertically. Does anyone familiar with the plugin know what to do?