How do I add a Wordpress Install to "/blog" on my server when "/" serves a different app via NGINX?

To round this out, I’m posting the solution for prosperity. Even though @hansen didn’t post the final solution, they were crucial to figuring this out.

server {
    listen 80;
    listen [::]:80;
    server_name domain.org www.domain.org;
    return 301 https://$server_name$request_uri;
}

server {

    # SSL configuration

    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name www.domain.org domain.org;
    include snippets/ssl-domain.org.conf;
    include snippets/ssl-params.conf;

    access_log /home/user/logs/nginx/nginx-access.log;
    error_log  /home/user/logs/nginx/nginx-error.log;

    client_max_body_size 4G;

    root /home/user;

    keepalive_timeout 5;

    location = /favicon.ico { access_log off; log_not_found off; }

    location /static {
        alias /home/user/app/static;
    }


    location /uploads {
        alias /home/user/uploads;
    }

    error_page 500 502 503 504 /500.html;
    location = /500.html {
        alias /home/user/app/app/app/templates;
    }

    location / {
        include proxy_params;
        proxy_pass http://unix:/home/user/app/app.sock;
    }

    location ~ /.well-known {
        allow all;
    }

    location ^~ /blog {

        index index.php index.html index.htm index.nginx-debian.html;
        try_files $uri $uri/ /blog/index.php$is_args$args;

        location ~ \.php$ {
            include snippets/fastcgi-php.conf;
            fastcgi_pass unix:/run/php/php7.0-fpm.sock;
        }
    }
}