This is a nice study in words of medium length, as was dictated by the
two-ply “X” construction. The solver will observe that the central
interlock is of the good, familiar “L” joint sort.
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####| 1 | 2 | 3 | 4 |#####|#####|#####|#####|#####| 5 | 6 | 7 | |#####|
|#####| | | | |#####|#####|#####|#####|#####| | | | |#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 8 |#####| 9 | | | 10 |#####|#####|#####| 11 | | | |#####| 12 |
| |#####| | | | |#####|#####|#####| | | | |#####| |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 13 | 14 |#####| 15 | | | 16 |#####| 17 | | | |#####| 18 | |
| | |#####| | | | |#####| | | | |#####| | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 19 | | 20 |#####| 21 | | | 22 | | | |#####| 23 | | |
| | | |#####| | | | | | | |#####| | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 24 | | | 25 |#####| 26 | | | | |#####| 27 | | | |
| | | | |#####| | | | | |#####| | | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####| 28 | | | 29 |#####| 30 | | |#####| 31 | | | |#####|
|#####| | | | |#####| | | |#####| | | | |#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####|#####| 32 | | | 33 | |#####| 34 | 35 | | | |#####|#####|
|#####|#####| | | | | |#####| | | | | |#####|#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####|#####|#####| 36 | | |#####|#####|#####| 37 | | |#####|#####|#####|
|#####|#####|#####| | | |#####|#####|#####| | | |#####|#####|#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####|#####| 38 | | | | 39 |#####| 40 | | | | 41 |#####|#####|
|#####|#####| | | | | |#####| | | | | |#####|#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####| 42 | | | |#####| 43 | 44 | |#####| 45 | | | 46 |#####|
|#####| | | | |#####| | | |#####| | | | |#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 47 | | | |#####| 48 | | | | 49 |#####| 50 | | | 51 |
| | | | |#####| | | | | |#####| | | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 52 | | |#####| 53 | | | | | | 54 |#####| 55 | | |
| | | |#####| | | | | | | |#####| | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| 56 | |#####| 57 | | | |#####| 58 | | | 59 |#####| 60 | |
| | |#####| | | | |#####| | | | |#####| | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| |#####| 61 | | | |#####|#####|#####| 62 | | | 63 |#####| |
| |#####| | | | |#####|#####|#####| | | | |#####| |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|#####| 64 | | | |#####|#####|#####|#####|#####| 65 | | | |#####|
|#####| | | | |#####|#####|#####|#####|#####| | | | |#####|
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+