Build me some string stairs
Charcoal, 22 bytes

Ｆ⪪θ «↑⸿⸿ＦＬι«Ｍ¬﹪κＩη↙§ικ


Try it online! Link is to verbose version of code. Explanation:

  θ                      First input
 ⪪                      Split on spaces
Ｆ   «                   Loop over each word
     ↑⸿⸿                Move the cursor to the top row and two columns right*
          ι             Current word
         Ｌ              Length
        Ｆ  «            Loop over implicit range
               κ        Current index
                 η      Second input
                Ｉ       Cast to integer
              ﹪         Modulo
             ¬          Logical not
            Ｍ     ↙     Move that many characters down and left
                    ι   Current word
                     κ  Current index
                   §    Index into word and implicitly print


*More precisely, "move to the start of the next line twice, but as if the canvas was rotated." Edit: In between this challenge being set and this answer being accepted, Charcoal actually acquired a means of splitting a string into pairs of characters, reducing the code 16 bytes:
Ｆ⪪θ «↑⸿⸿Ｆ⪪ιＩη«κ↙ Try it online! Link is to verbose version of code. Explanation:

  θ                 First input
 ⪪                  Split on spaces
Ｆ   «               Loop over each word
     ↑⸿⸿            Move the cursor to the top row and two columns right
          ι         Current wordＩη
            η       Second input
           Ｉ        Cast to integer
         ⪪          Split into substrings of that length
        Ｆ    «      Loop over each substring
              κ     Print the substring
               ↙    Move the cursor down and left