CL-USER> (with-open-file (stream #p"/tmp/bytes" :element-type '(unsigned-byte 8)
                                                :direction :input)
           (let ((flexi-stream (flex:make-flexi-stream stream :position 0 :bound 4
                                                              :element-type '(unsigned-byte 8)))
                 (output (make-array 10 :initial-element 0)))
             (read-sequence output flexi-stream)
             output))
#(0 1 2 3 0 0 0 0 0 0)
CL-USER> (with-open-file (stream #p"/tmp/bytes" :element-type '(unsigned-byte 8)
                                                :direction :input)
           (let ((flexi-stream (flex:make-flexi-stream stream :position 4 :bound 4
                                                              :element-type '(unsigned-byte 8)))
                 (output (make-array 10 :initial-element 0)))
             (read-sequence output flexi-stream)
             output))
#(0 0 0 0 0 0 0 0 0 0)
CL-USER> (with-open-file (stream #p"/tmp/bytes" :element-type '(unsigned-byte 8)
                                                :direction :input)
           (let ((flexi-stream (flex:make-flexi-stream stream :position 4 :bound 8
                                                              :element-type '(unsigned-byte 8)))
                 (output (make-array 10 :initial-element 0)))
             (read-sequence output flexi-stream)
             output))
#(0 1 2 3 0 0 0 0 0 0)