Snowflake: 0-indexed from, EXCLUSIVE upper to  →  Python arr[from:to]
  DuckDB:    1-indexed from, INCLUSIVE upper to  →  SQL standard arr[from..to]

Transpilation:
 python -m sqlglot --read snowflake --write duckdb "SELECT ARRAY_SLICE([1,2,3,4,5], 1, 3) AS sf_1_3, ARRAY_SLICE([1,2,3,4,5], 0, 3) AS sf_0_3, ARRAY_SLICE([1,2,3,4,5], 2, 5) AS sf_2_5, ARRAY_SLICE([1,2,3,4,5], 0, 0) AS sf_0_0, ARRAY_SLICE([1,2,3,4,5], NULL, 3) AS sf_null_from, ARRAY_SLICE([1,2,3,4,5], 1, NULL) AS sf_null_to, ARRAY_SLICE([0,1,2,3,4,5,6], 0, -2) AS sf_pos_neg, ARRAY_SLICE([0,1,2,3,4,5,6], -5, -3) AS sf_both_neg, ARRAY_SLICE(['a','b','c','d'], -2, -1) AS sf_neg_idx, ARRAY_SLICE(NULL, 1, 3) AS sf_null_arr, ARRAY_SLICE([], 1, 3) AS sf_empty_arr" 2>&1 | grep -v UserWarning | grep -v warnings.warn
SELECT
  ARRAY_SLICE([1, 2, 3, 4, 5], 2, 3) AS "sf_1_3",
  ARRAY_SLICE([1, 2, 3, 4, 5], 1, 3) AS "sf_0_3",
  ARRAY_SLICE([1, 2, 3, 4, 5], 3, 5) AS "sf_2_5",
  ARRAY_SLICE([1, 2, 3, 4, 5], 1, 0) AS "sf_0_0",
  ARRAY_SLICE([1, 2, 3, 4, 5], CASE WHEN NULL >= 0 THEN NULL + 1 ELSE NULL END, 3) AS "sf_null_from",
  ARRAY_SLICE([1, 2, 3, 4, 5], 2, CASE WHEN NULL < 0 THEN NULL - 1 ELSE NULL END) AS "sf_null_to",
  ARRAY_SLICE([0, 1, 2, 3, 4, 5, 6], 1, -3) AS "sf_pos_neg",
  ARRAY_SLICE([0, 1, 2, 3, 4, 5, 6], -5, -4) AS "sf_both_neg",
  ARRAY_SLICE(['a', 'b', 'c', 'd'], -2, -2) AS "sf_neg_idx",
  ARRAY_SLICE(NULL, 2, 3) AS "sf_null_arr",
  ARRAY_SLICE([], 2, 3) AS "sf_empty_arr"
  
  Duckdb:
  │ sf_1_3  │  sf_0_3   │  sf_2_5   │ sf_0_0  │ sf_null_from │ sf_null_to │   sf_pos_neg    │ sf_both_neg │ sf_neg_idx │ sf_null_arr │ sf_empty_arr │
│ int32[] │  int32[]  │  int32[]  │ int32[] │   int32[]    │  int32[]   │     int32[]     │   int32[]   │ varchar[]  │    int32    │   int32[]    │
├─────────┼───────────┼───────────┼─────────┼──────────────┼────────────┼─────────────────┼─────────────┼────────────┼─────────────┼──────────────┤
│ [2, 3]  │ [1, 2, 3] │ [3, 4, 5] │ []      │ NULL         │ NULL       │ [0, 1, 2, 3, 4] │ [2, 3]      │ [c]        │    NULL     │ []           │
└─────────┴───────────┴───────────┴─────────┴──────────────┴────────────┴─────────────────┴─────────────┴────────────┴─────────────┴──────────────┘